Objective: To compare the efficacy of the classic treatment of ocular toxoplasmosis (pyrimethamine, sulfadiazine, and prednisolone) with a regimen consisting of trimethoprim/sulfamethoxazole (co-trimoxazole) plus prednisolone. Design: Prospective randomized single-blind clinical trial. Participants: Fifty-nine patients with active ocular toxoplasmosis were randomly assigned to 2 treatment groups: 29 were treated with pyrimethamine/sulfadiazine, and 30 patients received trimethoprim/ sulfamethoxazole. Intervention: Treatment consisted of 6 weeks’treatment with antibiotics plus steroids. Antitoxoplasmosis antibodies (immunoglobulinMIgM and IgG) were measured using an enzyme-linked immunosorbent assay. Main Outcome Measures: Changes in retinochoroidal lesion size after 6 weeks’treatment, visual acuity (VA) before and after intervention, adverse drug reactions during follow-up, and rate of recurrence. Results: Active toxoplasmosis retinochoroiditis resolved in all patients over 6 weeks’treatment, with no signifi-cant difference in mean reduction of retinochoroidal lesion size between the 2 treatment groups (61%reduction in the classic treatment group and 59%in the trimethoprim/ sulfamethoxazole group, P=0.75). Similarly, no significant difference was found in VA after treatment between the 2 groups (mean VAs after treatment were 0.12 logarithm of the minimum angle of resolution logMAR 20/25 in the classic treatment group and 0.09 logMAR 20/25 in the trimethoprim/ sulfamethoxazole group, P=0.56). Adverse effects were similar in both groups, with one patient in each suffering from any significant drug side effects. The overall recurrence rate after 24 months’follow-up was 10.16%, with no significant difference between the treatment groups (P=0.64). Conclusions: Drug efficacies in terms of reduction in retinal lesion size and improvement in VA were similar in a regimen of trimethoprim/sulfamethoxazole and the classic treatment of ocular toxoplasmosis with pyrimethamine and sulfadiazine. Therapywith trimethoprim/sulfamethoxazole seems to be an acceptable alternative for the treatment of ocular toxoplasmosis. Objective: To compare the efficacy of the classic treatment of ocular toxoplasmosis (pyrimethamine, sulfadiazine, and prednisolone) with a regimen consisting of trimethoprim / sulfamethoxazole plus prednisolone. Design: Prospective randomized single-blind clinical trial. Participants: Fifty -nine patients with active ocular toxoplasmosis were randomly assigned to 2 treatment groups: 29 were treated with pyrimethamine / sulfadiazine, and 30 patients received trimethoprim / sulfamethoxazole. Intervention: Treatment consisted of 6 weeks’treatment with antibiotics plus steroids. Antitoxoplasmosis antibodies (immunoglobulinMIgM and IgG) were measured using an enzyme-linked immunosorbent assay. Main Outcome Measures: Changes in retinochoroidal lesion size after 6 weeks’ treatment, visual acuity (VA) before and after intervention, adverse drug reactions during follow-up, and rate of recurrence. Results: Active toxoplasmosis retinochoroiditis resolved in all patients over 6 weeks ’treatment, with no signifi-cant difference in mean reduction of retinochoroidal lesion size between the 2 treatment groups (61% reduction in the classic treatment group and 59% in the trimethoprim / sulfamethoxazole group, P = 0.75). Similarly, no significant difference was found in VA after treatment between the 2 groups (mean VAs after treatment were 0.12 logarithm of the minimum angle of resolution log MAR 20/25 in the classic treatment group and 0.09 log MAR 20/25 in the trimethoprim / sulfamethoxazole group, P = 0.56) The overall recurrence rate after 24 months’ follow-up was 10.16%, with no significant difference between the treatment groups (P = 0.64) . Conclusions: Drug efficacies in terms of reduction in retinal lesion size and improvement in VA were similar in a regimen of trimethoprim / sulfamethoxazole and the classic treatment of ocular toxoplasmosis with pyrimetha mine andsulfadiazine. Therapy with trimethoprim / sulfamethoxazole seems to be an acceptable alternative for the treatment of ocular toxoplasmosis.