A retrospective study of 112 patients with septic arthritis (SA) caused by pyogenic organisms and fungi attended at the same Medical Service from 1975 to 1994. This SA was more common among male patients and the age at onset of disease was 42 +/- 23.2 years. Predisposing factors were identified in 53 patients, the more common being connective tissue diseases and parenteral drug abuse (PDA). The main portal of entry was bacteremia from a distant infective source. The most common causative agents were Grampositive cocci (particularly S. aureus) and the more uncommon organisms were recovered from patients with underlying diseases. The diagnostic delay was 14.1 +/- 28.1 days. Single joint SA occurred in 88% of patients. Large joints were mainly involved. On admission, 25% of patients had no fever and only 54% of them had leukocytosis; therefore, the lack of these findings in a given patient with acute arthritis should not rule out the possibility of SA. Initial therapy consisted of daily arthrocentesis and i.v. antibiotics. The mean duration of antibiotic therapy was 47 +/- 23 days; the duration of the i.v. route was 23 +/- 14 days. An eighty percent of patients recovered without functional sequelae. The 31 patients who required surgical drainage had a longer diagnostic delay and a worse evolution, thus stressing the necessity of an early diagnosis. In the last decade (1986-1994) an increase in some predisposing factors (iatrogenic SA and PDA), a shorter diagnostic delay, a more prolonged antibiotic therapy, a smaller proportion of surgical drainage and an ultimate evolution identical to that in the previous decade were observed.