The relationship of major dietary carotenoids, preformed and total vitamin A, and different foods to serum beta-carotene and serum retinol levels was studied among 224 male and 117 female adults taken from the Finnish Mobile Clinic Health Examination Survey. Serum nutrients were analysed after 10-15 years of storage at -20 degrees C. Dietary data were collected by a quantitative dietary history interview method. Intakes of nutrients were calculated based on analysed data on Finnish foods. The positive gradient between beta-carotene intake and serum level, being highly significant in women and non-significant in men, was concentrated in non-smokers. Other major dietary carotenoids tended to be positively correlated with serum beta-carotene in parallel with dietary beta-carotene. Carrot intake was the most specific single food predictor for serum beta-carotene. Serum retinol levels were not significantly associated with dietary variables and were not affected by current smoking. In women, serum beta-carotene values were higher, but serum retinol levels lower, compared with men. The results support earlier findings that smoking modifies the association between dietary beta-carotene and serum beta-carotene, and suggest that despite the long storage of serum samples beta-carotene determinations had some value as a biological marker for beta-carotene in the diet.