Reports on the association between obesity and lymphohematopoietic malignancies (LHMs) have been inconsistent. The present study aimed at exploring this association for specific disease lymphohematopoietic entities in a large Norwegian cohort. Height and weight were measured in two million Norwegian men and women aged 20-74 years during 1963-2001. During follow-up, 24,500 cases of LHMs were observed. Relative risks of disease were estimated by Cox proportional hazards regression. The risk of LHMs overall increased moderately by increasing body mass index and height in both sexes. The relative risk of LHMs per five-unit increase in body mass index was 1.11 (95% confidence interval (CI): 1.08, 1.14) in men and 1.08 (95% CI: 1.05, 1.11) in women. For each 10-cm increase in height, the relative risk was 1.19 (95% CI: 1.16, 1.22) in men and 1.16 (95% CI: 1.12, 1.20) in women. Separate analyses for different lymphohematopoietic malignancies did not reveal any group's being particularly strongly associated with body mass index. A modest increase in the risk of LHMs combined was observed with increasing height. The moderate associations between height and body mass index and LHMs found in the present study indicate that the observed increase in overweight/obesity plays only a minor role in explaining the increase in the incidence of LHMs.