Summan Previous cross-sectional data suggest a positive association between serum cholesterol and brain neoplasms. but the results of cohort studies are inconclusive. There is evidence that in women the growth of meningiomas and astrocytomas depends on the hormonal status. The present investigation comprised data on serum cholesterol and P-lipoprotein concentration among 229 participants in a health survey with subsequently diagnosed central nervous system (CNS) tumours. Data analyses included comparison of mean serum cholesterol and P-lipoprotein level between cases and randomly selected controls five for each case. matched for sex. age at screening and time of examination. The results showed a positive relation between the A-lipoprotein level and the development of a CNS tumour (benign or malignant) in women under 50 years of age. and a negative association in those of older age with development of malignant tumours. which implies a possible influence of the menopausal status. Repeating the computations after excluding cases diagnosed within 5 vears from screening revealed significant associations also between the serum cholesterol concentration and the development of a malignant CNS tumour, with a pattern similar to that of frlipoprotein. In conclusion, in women. irregular variation in the P-lipoprotein level. which is involved in the synthesis of progesterone in the CNS. may enhance oncogenic transformation of astrocytes and meningeal cells: however. transformation of the latter is restricted to vounger women.