Updated June 16, 2026
Section 6.56 in the Spotlight
The seventeenth edition of CMOS was the first edition to rule explicitly on whether “too” in the adverbial sense of “also” should be set off by commas. The rule, which remains unchanged for the eighteenth edition, applies also to “either,” which as an adverb can play a similar role in a sentence or clause.
The short answer is that commas are usually unnecessary but occasionally helpful for emphasis or clarity. We can find out what this means in practice—and why having a rigid rule isn’t a good idea—by starting with a simple example.
The first edition of the Manual, published in 1906, may not have addressed “too” or “either” by name, but it did have something to say about such words. Paragraph 132 ended with a suggestion that commas should not be used “ordinarily with such terms as ‘perhaps,’ ‘also,’ ‘likewise,’ etc.”—and offered a few examples in support of this.
Here’s the last one: “He was a scholar and a sportsman too.” Note the absence of any comma. And though it wasn’t featured in the examples, the word “either” would play the same role in such a sentence rewritten in the negative: “He wasn’t a scholar or a sportsman either.”
Whatever else you might think of that ancient example from the first edition, it does provide the basis for a rule—or in this case a sort of nonrule.
What Was That Rule Again?
It’s tempting to assume that whether to set off “too” or “either” with commas would depend on its relationship to the rest of the sentence. According to this assumption, a comma would be required in that example from 1906 if “too” applied to “sportsman” but not if it referred to the subject “He” (or to the sentence as a whole).
Or would it be the other way around?
That’s a serious question, because such a rule would require an agreement between writers and readers on precisely how to interpret what the presence or absence of a comma means.
Let’s say there is such an agreement. Then the following sentence—with a comma before “too”—would mean that the subject “She” is not only a scholar but also an athlete (we’ve updated the original sentence), with the emphasis on “athlete”:
She is a scholar and an athlete, too.
Applying that same logic, removing the comma would shift the emphasis to the subject “She.” In that case, some previously mentioned other person or persons are scholars and athletes, and “She” is a scholar and an athlete just like that person or those people:
She is a scholar and an athlete too.
You could extend this logic to “either” by rewriting the sentence in the negative: “She wasn’t a scholar or an athlete either.” That would put the emphasis on “She”; adding a comma would move the emphasis to “athlete”: “She wasn’t a scholar or an athlete, either.”
Makes sense, right? Yes, maybe—except there is no such agreement.
Context Is Everything
When it comes to making meaning, context is almost always more important than commas. This is particularly true with “too” and “either.” If your sentence is not entirely clear from context alone, revise until it is.
In the following example, it’s clear from context that “too” refers to “athlete”:
Maria’s academic achievements are well known, but she also excelled at track and field. Maria was a scholar and an athlete too.
But in this example of quoted dialogue (as in fiction), the context makes it clear that “too” refers back to “Maria”:
“All my eleven kids got perfect grades while excelling at sports.”
“Maria was a scholar and an athlete too,” I reminded her, making a plug for my daughter.
In either case, a comma would have made no appreciable difference to the meaning, which is predetermined in both examples by the context.* (Again, you can make the examples negative to test “either.”)
In other words, you can usually either omit or add commas around “too” or “either” when either word is used like “also,” regardless of the sentence.
Italics and Word Order
Where a particular emphasis is important, and you don’t want to leave it to context alone, one option is to apply italics. Italics will help readers decode the intended meaning, or at least the intended emphasis.
Add commas to the following examples if you like, but they won’t change the meaning of either version even if they could:
Maria was a scholar and an athlete too.
Maria was a scholar and an athlete too.
Another option that works well with “too” (but rarely with “either”) is to shift the placement of the adverb. In the following example, it’s obvious that “too” applies to Maria:
Maria too was a scholar and an athlete.
Commas lend an additional dimension to this sentence:
Maria, too, was a scholar and an athlete.
Those commas, by drawing attention to the word “too,” emphasize the rhetorical shift implied by that word. Especially when “too” occurs midsentence, such commas may add a bit of clarity also.
Summing It Up
Some writers follow a simple rule: Use commas with “too” and “either” whenever these words are used in the sense of “also.” And because such commas don’t have the power to determine the intended meaning all by themselves, this approach is fine.
Especially if you’re an editor working with an author whose style features frequent, well-placed commas (in what is sometimes called close rather than open punctuation), you should query before simply removing them.
But in general, Chicago favors a relatively spare, open approach to commas, omitting many commas that aren’t necessary for comprehension—including commas with “too” and “either.”
If that’s you too, then you won’t need those commas either.
In sum, the key to deciding when to use commas with “too” and “either”—and the spirit of the rule in paragraph 6.56—is to leave them out by default. Then add them rarely if at all—and only where a bit of extra emphasis or clarity seems warranted.
* It may go without saying, but the functionally similar word “also” is almost never set off by commas: “She was a scholar and an athlete also.” This is perhaps the strongest argument for not requiring commas with “too” and “either.”
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