Background: Graft-versus-host-disease (GvHD) occurs in one third or eve n half of bone marrow transplant (BMT) patients, involving three major target or gans: gut, liver and skin. Objectives: The histopathological and immunohistochem ical features of normal-looking skin in oncohaematological patients on day 100 after BMT were studied to find a possible relationship between the histopatholo gical findings and clinical variables (history or clinical evidence of GvHD, pre vious therapeutic regimens or infections). Methods: Fifty-one Caucasian oncoha ematological patients, who had had an allogenic BMT, had a biopsy taken from nor mal-looking skin in nonsun-exposed areas (buttocks or the lumbar region), ar ound the 100th day after BMT. The histology was studied, and the influence of cl inical variables on the development of every different histopathological pattern was evaluated through statistical analysis. Results: Histopathological analysis based on morphological criteria revealed the presence of three different patter ns: a postinflammatory pattern (45% ), changes similar to grade I and II of GvH D (31% ) and no significant changes (24% ). Statistical analysis revealed that only the presence of peaks of cytomegalovirus (CMV) antigen in the blood within 100 days from BMT was significantly associated with the pattern of GvHDlike cha nges. Conclusions: Normal-looking skin in 76% of BMT patients is not necessa rily histologically normal. The pattern with more prominent changes, the GvHD- like pattern, has been found to be associated with a more frequent history of CM V antigen in the blood within 100 days from BMT. Background: Graft-versus-host-disease (GvHD) occurs in one third or eve n half of bone marrow transplant (BMT) patients, involving three major targets or gans: gut, liver and skin. Objectives: The histopathological and immunohistochemical features of normal-looking skin in oncohaematological patients on day 100 after BMT were studied to find a possible relationship between the histopatholo gical findings and clinical variables (history or clinical evidence of GvHD, pre vious therapeutic regimens or infections). Methods: Fifty-one Caucasian oncoha ematological patients, who had had an allogenic BMT, had a biopsy taken from nor mal-looking skin in nonsun-exposed areas (buttocks or the lumbar region), ar ound the 100th day after BMT. The histology was studied, and the influence of cl inical variables on the development of every different histopathological pattern was evaluated through statistical analysis. Results: Histopathological analysis based on morphological criteria revealed the pr esence of three different patters ns: a postinflammatory pattern (45%), changes similar to grade I and II of GvH D (31%) and no significant changes (24%). Statistical analysis revealed that only the presence of peaks of cytomegalovirus CMV) antigen in the blood within 100 days from BMT was significantly associated with the pattern of GvHD like changes. Conclusions: Normal-looking skin in 76% of BMT patients is not necessa rily histologically normal. The pattern with more prominent changes, the GvHD - like pattern, has been found to be associated with a more frequent history of CM V antigen in the blood within 100 days from BMT.