Patients receive induction therapy with intravenous ganciclovir or foscarnet daily for 14 days, then are placed on standard maintenance therapy with the induction drug for at least 11 months or until progression. Patients are randomized to receive 1 of 2 doses of MLS 109 or placebo every 2 weeks during induction and maintenance. They are followed at weeks 2 and 4 and every 4 weeks thereafter for 40 weeks. Patients who have not progressed by week 40 continue study drug with follow-up every 2 months until CMV progression occurs. AS PER AMENDMENT 11/29/96: Enrollment onto the current study has been discontinued. To study the enhancement of humoral immunity, a high-dose cohort has been added. Patients are now randomized to MSL 109 given at a higher dose or placebo administered at the same intervals as before. Randomization is weighted 2:1 in favor of high-dose MSL 109. Interim analyses will be performed to provide for early discontinuation, as indicated. Patients randomized under earlier versions may continue on their original study assignment if a study endpoint has not been reached.