We studied infections in 101 consecutive patients who underwent liver transplantation between July 1984 and September 1985. The mean length of follow-up was 394 days. Eighty-three percent of population had 1 or more episodes of infection and 67% of the population had severe infections. The overall mortality was 26/101 (26%) and 23 of 26 deaths (88%) were associated with infection. Seventy percent of severe infections occurred in the first 2 months after transplantation. The most frequent severe infections were abdominal abscess, bacterial pneumonia, invasive candidiasis, Pneumocystis pneumonia, and symptomatic cytomegalovirus infection. Patients with more than 12 hours of cumulative surgical time had a higher rate of severe infections (P less than 0.001), particularly fungal (P less than 0.001) and bacterial (P less than 0.01) infections. Also, the use of choledocho-jejunostomy was associated with a higher rate of infection in patients who had more than 1 transplant operation (P less than 0.02). No increase in infection was found in patients who received azathioprine, or more than the median number of steroid boluses or "recycles"; but patients who received OKT3 therapy had a higher rate of protozoal infections (P less than 0.05). A result similar to that of our previous studies was a strong relation between the number of severe fungal infections and prolonged courses of antibiotics after transplant operation (P less than 0.001). Pretransplant manifestations of severe liver disease such as ascites, encephalopathy, and gastrointestinal bleeding were not associated with higher rates of infection after transplantation, but high serum levels of ALT were. Patients with lower ratios of T-helper to T-suppressor lymphocytes had more severe viral (P less than 0.02) and fungal (P less than 0.01) infections after transplantation.