The authors report a 58-year-old female who originally presented with acquired pure red cell aplasia (PRCA). At diagnosis, the karyotype was normal, the serum erythropoietin level was highly elevated and no T-cell mediated inhibition of erythropoiesis was demonstrated in coculture studies. Conventional immunosuppressive therapy proved ineffective. A year later a diagnosis of hyperfibrotic myelodysplastic syndrome was assessed. The sequential bone marrow examinations in the course of the three years showed a progressive increase in bone marrow fibrosis, erythroid hyperplasia and dysmegakaryocytopoiesis, terminating in the acute myeloid leukemia. This sequence of the events included the appearance of del(5)(q13q33), four years after setting a diagnosis of PRCA. The authors suggest that the absence of both cytogenetic abnormality and the signs of dyshematopoiesis at the diagnosis of PRCA does not exclude ultimately a "clonal" category of the disease. Thus, repeated hematological and cytogenetical reevaluations are recommended.