Ganciclovir and Foscarnet were compared in an open randomised trial as treatment and secondary prophylaxis of cytomegalovirus (CMV) retinitis in patients with AIDS. Patients responded more rapidly to Ganciclovir than to Foscarnet although eventual response rates were similar with both drugs. During maintenance therapy there were trends towards more delayed reactivation of CMV and fewer adverse events requiring changes in therapy, in the Ganciclovir group. However, these patients had more line infections and a higher blood transfusion requirement.