To evaluate the relation of PML/RARalpha isoforms in adult APL patients to clinical therapy and prognosis, the picture of blood and bone marrow aspirates for 71 APL patients treated by induction therapy were peridically examined and the different transcripts of PML/RARalpha were assayed by nested RT-PCR. The results showed that the median WBC count (x 10(9)/L) in the patients with the short (S) and variable (V) isoform were significantly higher than that in long (L) isoform. So, the serious bleeding complications early occurred. Relapse risk for patients with S and variable isoforms were higher than that with L isoform. In conclusion, PML/RARalpha isoforms in patients with APL may be the independent prognostic factor.