We conducted a longitudinal study of five patients with anterior and posterior acute toxoplasmic uveitis to determine the relationships, if any, between the level of toxoplasmic activity, therapy, and serum antibody titers to retinal proteins. All patients showed increased serum antibody responses to S-, P-, or p59ag-antigen isolated from bovine retina. The titers to S-antigen tended to decrease with clinical improvement and stabilized at titers somewhat higher than normal; the anti-p59ag titers decreased in those patients treated with clindamycin and sulfadiazine and remained increased throughout the acute attack and remained increased even after the attack ended.