The biological mothers of 23 patients presenting with acute chorioreti
nal toxoplasmosis had sera screened for the presence of antibodies to
Toxoplasma gondii. Twenty-two of the mothers (96%) had positive serolo
gy and one (4%) had negative serology. This is consistent with the hyp
othesis that most cases of ocular toxoplasmosis are congenital in orig
in, but indicates that some cases are due to acquired toxoplasmosis.