In amsart, I used


to change the Proof heading from italics to boldface. However, when I write, for instance,

\begin{proof}[Proof of X's Lemma]

I get the output Proof of X's Lemma in italics and not in boldface. How can I fix this (and possibly improve the trick above)?

  • 1
    not directly relevant to the question, but ... the features of amsthm are built into amsart (and all the ams document classes), so it isn't necessary to specify that with \usepackage, and doing that has no effect. Sep 25, 2015 at 16:08

1 Answer 1


One option is to patch \proof to substitute \itshape for \bfseries:





\begin{proof}[A test proof]


enter image description here

If you don't want the period after the head in bold-face font, the patch would be


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