BACKGROUND: Bone marrow biopsies following the completion of remission-induction chemotherapy for patients of acute myelogenous leukemia (AML) whose blasts on bone marrow smear are counted less than 5%, show abnormal localization of immature precursors (the so-called ALIP defined as clusters or aggregates of small mononuclear elements with a narrow rim of light blue stained agranular cytoplasm) occasionally. The importance of ALIP in bone marrow section after antileukemic therapy is not determined yet. The purpose of this study is to elucidate the significance of ALIP on patients' remission duration and survival. METHODS: The bone marrow slides from adult AML patients who achieved complete remission (CR) after receiving first antileukemic therapy between January 1987 and April 1996 in Seoul National University Hospital were reviewed. Among them, 24 patients showed ALIP findings in their bone marrow biopsy sections and 8 patients' bone marrow were rebiopsied before next chemotherapy.We analyzed them on the histopathologic aspects. The patients who achieved CR after receiving first antileukemic therapy using Ara- C and daunorubicin were analyzed about their remission duration and survival duration according to ALIP positiveness (ALIP+ group : 16 patients, ALIP- group : 39patients. RESULTS: 1) Among eight rebiopsied bone marrow sections, six patients showed disappearance of ALIP findings spontaneously and none showed the increase of blast counts more than 5%.2) No statistically significant difference about patient characteristics between ALIP+ group and ALIP- group was shown except intervals between first antileukemic chemotherapy and biopsy of bone marrow (ALIP+ vs. ALIP-, 28 days vs. 34 days, P=0.001). The actuarial risk of relapse and CR duration were similar in both groups (P=0.44). The median duration of remission for the ALIP+ patients was 7 months and 12 months for ALIP- patients. Also the overall survival was similar in both groups (P=0.37). The median duration ofsurvival was 12 months for ALIP+ patients and 21 months for ALIP- patients. CONCLUSION: We did not find any statistically significant differences between ALIP+ group and ALIP- group for remission duration and overall survival, and observed ALIP findings in earlier bone marrow biopsies afterchemotherapy. We concluded ALIP findingmight be a indirect evidence of bone marrow regeneration, but further studies with cytogenetics or FISH method should be followed.