• Forty-eight patients with arthritis and meningitis were identified by hospital chart review among 2,089 cases of bacterial meningitis treated between 1969 and 1984. The etiologic agents were Haemophilus Influenzae in 38 cases (79%), Neisseria meningitidis in nine cases (19%), and Staphylococcus aureus in one case (2%). Thirteen patients had more than one joint affected: two affected joints, ten patients; three affected joints, two patients; and four affected joints, one patient. The elbow (34%) and knee (29%) were most frequently affected. Joint-fluid aspirations were done in 44 patients; 22 cases (50%) had bacteria or bacterial antigen identified In joint fluid by culture, Gram's stain, or counter-immunoelectrophoresis: H Influenzae (20 cases), N meningitidis (one case), and S aureus (one case). Of the 48 patients, 14 patients were noted to have arthritis at the time of diagnosis of meningitis, 16 patients on the first to sixth day, and 17 patients on the seventh day of treatment or later; one patient developed arthritis 12 days after treatment of H influenzae meningitis had been stopped. Fourteen cases with a culture-proved bacterial etiology of the arthritis developed arthritis within four days of treatment; the exception was a patient who developed arthritis after treatment of meningitis was stopped. Of the 21 patients with culture-negative joint fluid and who developed arthritis later In the course of treatment, 19 patients were considered to have possible immune complex arthritis. Management consisted of antibiotic therapy in all patients, open incision and drainage in 17 patients (36%), and multiple aspirations in 12 patients (25%). Of the remaining 19 patients, 15 patients had a single arthrocentesis performed and four patients had no aspiration. Early-onset arthritis appeared to be related to bacteremia whereas late-onset arthritis may be immune complex mediated.