The safety and efficacy of a 10-day course of ganciclovir therapy was assessed in 17 consecutive patients with proven cytomegalovirus infection. The patients were receiving immunosuppressive therapy for a variety of non-malignant renal conditions, including renal transplantation (seven patients), small vessel vasculitis (six patients), systemic lupus erythematosus (three patients) and Goodpasture's disease (one patient). Fifteen patients were pyrexial at the time of their cytomegalovirus infection. Twelve patients had pneumonitis manifesting as a pulmonary parenchymal infiltrate or a reduction in gas transfer. Fourteen patients had a significant lymphopenia (lymphocyte count less than 1 x 10(9)/l), nine were leucopenic (white cell count less than 3.5 x 10(9)/l) and nine had abnormal liver biochemistry. One patient had an infection of the ileum and one an infection of the larynx. All these disease manifestations responded completely to a single course of ganciclovir therapy. There were no clinical relapses and no side effects were observed. Ganciclovir is a safe and effective therapy when administered early in the course of cytomegalovirus infection in immunosuppressed patients with renal impairment.