The study was undertaken to determine the intake of vitamin A and C and plasma concentrations of these vitamins among in-school adolescents. The factors affecting the vitamin status of these adolescents were also determined. Data for this report were obtained from a cross-sectional survey of 600 in-school adolescents in Nsukka local government area (LGA) of Enugu State, Nigeria. Ninety and 45 of the adolescents were randomly selected for determining plasma concentrations of vitamin A and C and intake of these vitamins respectively. Dietary assessment was done using a three-day weighed food intake method. Venous blood samples were collected and used for determining plasma vitamin A using the trifluoroacetic acid (TFA) method, while plasma vitamin C was determined by the thiourea method. Values obtained were matched against standards. The intake of vitamin A by all the adolescents was adequate (126-137% of recommended intake), while the intake of vitamin C was inadequate (51-91% of recommended intake). The mean intake of vitamin C was higher among males (23.7 +/- 0.71-27.3 +/- 8.0) than among females (15.3 +/- 2.8-19.5 +/- 5.1). Despite the adequate intake of vitamin A, 40% of the male and 32% of the female adolescents had low plasma concentrations of the vitamin (< 20 microg/dL). On the other hand, concentrations of plasma vitamin C were low among about 47% of these adolescents. Using multiple regression analysis, the two most important variables influencing vitamin A status were household size (b = -0.629; p < 0.0 1) and nutrition knowledge (b = -1.372; p < 0.01), while for vitamin C status, these were household size (b = -0.110; p = 0.05) and age (b = 0.226; p < 0.05). The daytime students had a significantly (p < 0.05) better vitamin A and C status than the boarders. The prevalence of vitamin A and C deficiencies among the adolescents may be more than estimated due to inadequate intake and/or poor bioavailability. This may pose a serious health risk for adolescents. There is, therefore, a need for adequate nutrition education and awareness about healthy lifestyles among Nigerian adolescents.