The HPCRT was a multicenter, randomized, controlled clinical trial of cidofovir for the treatment of CMV (cytomegalovirus) retinitis. Patients with small peripheral CMV (cytomegalovirus) retinitis lesions (i.e., not at risk of immediate loss of visual acuity) were randomized to immediate treatment with cidofovir or deferred therapy until the retinitis had progressed. Patients randomized to immediate therapy received either 1) low-dose cidofovir at 5 mg/kg once weekly induction for 2 weeks, followed by 3 mg/kg once every 2 weeks for maintenance or 2) high-dose cidofovir at 5 mg/kg once weekly induction for 2 weeks followed by 5 mg/kg once every 2 weeks for maintenance. Patients whose retinitis progressed were given treatment according to best medical judgement, and those assigned to deferral were generally treated with cidofovir.