To determine the pharmacokinetics (blood levels) of three dose treatment plans of oral ganciclovir during a 28-day dosing period. Other purposes of the study are to determine in a population of HIV seropositive persons with cytomegalovirus (CMV) viremia, the safety, tolerance, and patient acceptability of oral ganciclovir given for 28 days, to collect preliminary laboratory evidence for antiviral activity and effectiveness of three dose regimens of oral ganciclovir based on blood and urine cultures of CMV, and to relate antiviral activity to dosage and to serum ganciclovir levels.