Imipenem/cilastatin sodium (IMP/CS) was administered to patients with severe infections complicated by hematological disorders and solid tumors to assess its efficacy and safety. Primary diseases in this series of 76 cases included 37 cases of hematological disorders (acute leukemia in 25 cases, malignant lymphoma in 7 cases, aplastic anemia in 3 cases and 2 other diseases) and 38 cases of solid tumors (lung cancer in 7 cases, gastric cancer in 11 cases, esophageal cancer in 6 cases, pancreatic cancer in 3 cases, bile duct cancer in 4 cases, hepatocellular cancer in 3 cases, and 4 other diseases). Following results were obtained. 1. Types of infection in hematological diseases were sepsis in 5 cases, suspected sepsis in 24 cases, pneumonia in 5 cases and 3 others. The efficacy rates were 100% in sepsis, 62.5% in suspected sepsis, 80% in pneumonia and 73% in all cases. 2. Types of infection in solid tumors were sepsis in 2 cases, suspected sepsis in 13 cases, pneumonia in 10 cases, cholecystitis in 2 cases, cholangitis in 5 cases, liver abscess in 2 cases, and 4 others. The efficacy rates were 50% in sepsis, 69.2% in suspected sepsis, 80% in pneumonia, and 71.1% in all cases. 3. IPM/CS was administered in single use in 66 cases and in combination with other antibiotics in 9 cases. The efficacy rate in the single use was 72.7% and that in the combination use was 66.7%. 4. The efficacy rate in 35 cases of first use was 71.4% and that in 40 cases of second use was 72.5%.(ABSTRACT TRUNCATED AT 250 WORDS)