The cellular immunoincompetence which follows bone marrow transplantation (BMT) allows both primary and reactivation infection with herpes viruses. We report the overall incidence and timing of varicella zoster virus (VZV) infections after BMT, including the clinical course, complications and associated clinical risk features. Of 1186 patients undergoing BMT through 1989, 216 patients developed VZV infection between 4 days and 10.8 years after BMT; 86% of them within the first 18 months. Of all patients transplanted, 15 +/- 3% by 6 months and 52 +/- 14% by 5 years had developed VZV infection. Dermatomal zoster represented 62% of the infections, while 32% had complicated VZV infection--CNS, disseminated or visceral zoster. All serious infections occurred within 7 months of BMT but only two patients died, both from VZV pneumonitis. Allogeneic and autologous recipients had a similar incidence of VZV infection. VZV seropositive patients had more frequent, earlier and often more complicated or disseminated infections. Age > or = 10 years and radiation in the pre-transplant conditioning were significantly and independently associated with higher rates of VZV infection within a multivariate regression model. Using this model, we could define clinical risk groups with distinctly different hazards of VZV infection: age > 10 years, radiation pre-BMT and VZV seropositive patients had a 44% incidence by 3 years versus age < 10 years, no radiation and VZV seronegative had a 0% incidence by 3 years. Acyclovir assigned for prophylaxis of CMV or HSV infection had no effect on the timing or incidence of VZV infection.(ABSTRACT TRUNCATED AT 250 WORDS)