The authors followed up 12 patients with dehiscences of surgical wounds and postoperative enterocutaneous fistulas treated by on a long-term basis by complete parenteral nutrition. Previous operations were performed on account of different non-tumorous (11/12) and tumourous (1/12) diseases of the gastrointestinal tract. Microbiological examinations were made in every patient on admission and during total parenteral nutrition, always once a week for a total period of 2-8 weeks (mean 4.4; median 4.5). The authors examined aerobic and facultatively anaerobic bacteria in smears from the fistulas, stomies, dehiscent surgical wounds and from the rectum. The findings did not confirm the suspicion of local nosocomial infection. Strikingly often bacteria producing indole were found (in 8/12 examined subjects) and/or bacteria with positive urease (12/12) and lecithinase activity (9/12 patients). In the detected strains of Pseudomonas aeruginosa (in 8/12 examined patients) lecithinase activity was confirmed in all. It cannot be ruled out that the above described enzymatic bacterial activities may have contributed to the failure of conservative therapy in the majority of patients (10/12).