Two groups of patients were administered either 4.5 X 10(6) U or 90 X 10(6) U each of recombinant DNA-derived interferon-beta serine (IFN-beta ser) i.v. daily for 10 days. IFN-beta ser affected lipoprotein lipids of patients in a dose dependent fashion. A decrease in plasma total cholesterol concentration occurred 24 h after therapy was initiated, regardless of dose. A dose-related decrease in plasma cholesterol concentration of 9% and 23% for patients on the low dose and high dose respectively occurred after 9 days of therapy. The plasma total cholesterol concentration decrease resulted primarily from a decrease in LDL cholesterol of 28% and 50% for patients on low and high doses respectively of IFN-beta ser. HDL-cholesterol was not significantly affected by IFN-beta ser administration. A dose-related increase in plasma triglyceride concentration occurred during IFN-beta ser, increasing 74% for patients on low dose and 136% for patients on high doses. This increase was only observed after 9 days on IFN-beta ser. Cholesterol reduction and triglyceride increases followed different time courses indicating different mechanisms may be involved.