Very few cases of human microsporidial infection have been reported. The advent of AIDS has changed this. There is increasing recognition that microsporidia are important opportunistic pathogens. However, the number of cases reported in the non-HIV population is small. We report here a case of microsporidial infection in a female patient with chronic myeloid leukemia undergoing allogeneic bone marrow transplantation. There was also an associated fungal infection. The diagnosis could be reached only after postmortem and was confirmed by electron micrography. We suggest that transplant patients are another group of patients who are susceptible to this group of opportunistic pathogens.