Objective To guide primary care physicians regarding the diagnosis and treatment of poststreptococcal reactive arthritis (PSReA) in adults. Patients and Methods We retrospectively reviewed an indexed database of all patients evaluated or hospitalized between 1976 and 1998 at Mayo Clinic Rochester and identified 35 patients with the diagnosis of reactive streptococcal arthritis, arthralgia, or arthritides. Twenty-nine patients with the diagnosis of acute rheumatic fever (ARF), septic streptococcal arthritis, or nonspecific reactive arthritis were excluded. Results PSReA was confirmed in 6 adults (3 women, 3 men; age range, 25–66 years). All patients were symptomatic with polyarthritis and oligoarthritis disproportionate to the objective findings on physical examination. Although all patients had negative throat cultures at the onset of arthritis, increased titers of anti-DNase B and antistreptolysin O confirmed recent streptococcal infection. Antecedent events included pharyngitis in 3 patients (who had received a minimum of a 10-day course of penicillin) and toxic shock syndrome in 1 patient. The latency of onset of arthritis ranged from 4 days to 6 weeks. The arthritic symptoms had a protracted course beyond the typical maximum of 3 weeks described for ARF. Treatment with aspirin did not provide symptomatic relief in any of the patients, whereas the response to therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) was at least partial in all cases. Symptomatic relief occurred in 1 patient who received indomethacin and in 1 patient treated with prednisone. Penicillin prophylaxis was recommended in 1 patient. Conclusion PSReA should be included in the differential diagnosis of all adult patients presenting with arthritis. Treatment strategies include aspirin, other NSAIDs, and corticosteroids. In adult patients with PSReA, there is no evidence to support the use of penicillin prophylaxis at this time. To guide primary care physicians regarding the diagnosis and treatment of poststreptococcal reactive arthritis (PSReA) in adults. We retrospectively reviewed an indexed database of all patients evaluated or hospitalized between 1976 and 1998 at Mayo Clinic Rochester and identified 35 patients with the diagnosis of reactive streptococcal arthritis, arthralgia, or arthritides. Twenty-nine patients with the diagnosis of acute rheumatic fever (ARF), septic streptococcal arthritis, or nonspecific reactive arthritis were excluded. PSReA was confirmed in 6 adults (3 women, 3 men; age range, 25–66 years). All patients were symptomatic with polyarthritis and oligoarthritis disproportionate to the objective findings on physical examination. Although all patients had negative throat cultures at the onset of arthritis, increased titers of anti-DNase B and antistreptolysin O confirmed recent streptococcal infection. Antecedent events included pharyngitis in 3 patients (who had received a minimum of a 10-day course of penicillin) and toxic shock syndrome in 1 patient. The latency of onset of arthritis ranged from 4 days to 6 weeks. The arthritic symptoms had a protracted course beyond the typical maximum of 3 weeks described for ARF. Treatment with aspirin did not provide symptomatic relief in any of the patients, whereas the response to therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) was at least partial in all cases. Symptomatic relief occurred in 1 patient who received indomethacin and in 1 patient treated with prednisone. Penicillin prophylaxis was recommended in 1 patient. PSReA should be included in the differential diagnosis of all adult patients presenting with arthritis. Treatment strategies include aspirin, other NSAIDs, and corticosteroids. In adult patients with PSReA, there is no evidence to support the use of penicillin prophylaxis at this time.