+@vindex ediff-ignore-case-option
+@vindex ediff-ignore-case-option3
+@vindex ediff-ignore-case
+Finally, Ediff can be told to ignore the case of the letters. This behavior
+can be toggled with @kbd{#c} and it is controlled with three variables:
+@code{ediff-ignore-case-option}, @code{ediff-ignore-case-option3}, and
+@code{ediff-ignore-case}.
+
+The variable @code{ediff-ignore-case-option} specifies the option to pass
+to the diff program for comparing two files or buffers. For GNU
+@code{diff}, this option is @code{"-i"}. The variable
+@code{ediff-ignore-case-option3} specifies the option to pass to the
+@code{diff3} program in order to make it case-insensitive. GNU @code{diff3}
+does not have such an option, so when merging or comparing three files with
+this program, ignoring the letter case is not supported.
+
+The variable @code{ediff-ignore-case} controls whether Ediff starts out by
+ignoring letter case or not. It can be set in @file{.emacs} using
+@code{setq-default}.
+
+When case sensitivity is toggled, all difference
+regions are recomputed.
+