Documented adverse reactions to anti-infective agents in patients of a home infusion company were studied to determine whether the prevalence of reactions was greater in patients receiving nafcillin or oxacillin than in those receiving other i.v. antiinfectives. Data on adverse drug reactions (ADRs) were obtained by reviewing the discharge summaries of all patients who received anti-infective therapy in 1990-1994 and the company's quarterly and annual ADR reports for that period. The occurrence of ADRs per total courses of therapy was calculated for groups of antiinfectives, as were intensity and causality. For ADRs to nafcillin and oxacillin, patient demographics and treatment information and outcomes were reviewed. A total of 2488 courses of anti-infective therapy were documented, and ADRs occurred in 10.9%. Nafcillin and oxacillin accounted for 105 courses, with an ADR rate of 31.4%; 99 patients received one of these drugs and 24 had ADRs, with rash and phlebitis the most common ADRs. Thirty-nine patients receiving nafcillin or oxacillin had documented infection with methicillin-sensitive Staphylococcus aureus. Seventy-five patients receiving nafcillin or oxacillin did not have an ADR; therapy was successful in 62 of these patients. Of the 24 patients with ADRs to nafcillin or oxacillin, 13 were switched to other i.v. anti-infectives, which were successful in 10 of them. Five patients were hospitalized because of ADRs to nafcillin or oxacillin. Most nafcillin or oxacillin ADRs that resulted in a therapy change or hospitalization occurred in the second or third week of therapy. Home care patients who received nafcillin or oxacillin therapy had a disproportionately high number of ADRs, compared with patients who received other anti-infective agents.