Thirty-five patients suffering from soft tissue infections (12), upper UTIs (6), bronchopneumonia (6), septicaemia (2), chronic osteomyelitis (2), intra-abdominal abscess (2), liver abscess (1), lung abscess (1), acute cholangitis (1), thoracic empyema (1) and chronic prostatitis (1) were given imipenem/cilastatin for 6-21 days. In 22 patients several aggravating factors coexisted, while infection in 16 patients was polymicrobial. The following pathogens were implicated: Pseudomonas aeruginosa (21), Escherichia coli (15), Enterobacter cloacae (6), Proteus spp. (3), Klebsiella pneumoniae(3), Citrobacter freundii (1), Salmonella enteritidis (1), Acinetobacter spp. (4), Haemophilus influenzae (2), Bacteroides fragilis (1) and Peptococcus saccharolyticus (1) with MICs to imipenem ranging between 0.5 and 8 mg/l. A successful clinical response was observed in 91.4% of the patients, while pathogens were eradicated in 75.9%, persisted in 24.2% and recurred, in 9.1% of patients, with development of resistance to imipenem in two Ps. aeruginosa strains. Against 150 multiresistant strains of Ps. aeruginosa, 40% of which were resistant to amikacin, 86.4% and 88.9% were found sensitive to ceftazidime and imipenem respectively. It is concluded that imipenem provides the possibility of treating successfully multiresistant and polymicrobial infections with a single antimicrobial.