The prognostic value of clinicopathological parameters, recorded at diagnosis, in idiopathic myelofibrosis (IMF) was retrospectively analyzed in a consecutive series of 32 patients followed for a minimum of 5 and maximum of 134 months in the period 1983-1994. Of the 32 patients, 18 were males and 14 were females. The mean age was 59.8 years (S.D., 10.4; range, 44-78 years). At the time of closure of the study (May 1995), 10 patients were dead, 18 were alive, and four were lost to follow up. The mean survival was 41 months (range 2-130 months).