Intrapleural streptokinase has been used in multiloculated empyemas to enhance pleural space drainage, presumably by causing fibrinolysis of the interlocular septae. We evaluated the efficacy and safety of daily administration of 10,000 U intrapleural streptokinase or equal volumes of saline to enhance resolution of experimental empyema in the rabbit pleural space. Seventy-two hours after intrapleural turpentine, 10(8) colony-forming units each of Escherichia coli, Peptostreptococcus anaerobius, and Bacteroides fragilis were injected into the sterile pleural effusion of all animals. Immediately after bacterial inoculation, and daily for 3 days, animals received 10,000 U streptokinase or saline intrapleurally. Animals that achieved a pleural fluid pH < 7.30 and either glucose < 50 mg/dl or LDH > 500 IU/L were included for data analysis. At Day 4 after bacterial inoculation, the streptokinase-treated empyemic rabbits had more pleural fluid (18.8 +/- 5.1 ml) (mean +/- SEM) than did saline-treated control animals (4.8 +/- 1.7 ml) (p = 0.015), fewer interpleural adhesions (8.2 +/- 2.7) than did saline-treated control animals (25.1 +/- 3.6) (p = 0.002), and comparable amounts of visceral and parietal pleural plaque than did saline-treated control animals (p = NS). No evidence of systemic fibrinolysis was observed at 1 h after intrapleural streptokinase administration. We conclude that intrapleural streptokinase decreases interpleural adhesion numbers but fails to reduce the amount of pleural plaque observed in experimental empyema in rabbits. The increases in pleural fluid volume observed after streptokinase administration may be due to mechanisms other than fibrinolytic activity.