Technical Abstract: Background: Beta-carotene (BC), beta-cryptoxanthin (CX) and alpha-carotene (AC) are common carotenoids that form vitamin A (VA). Conversion ratios for VA formation have been set at 12:1 for BC- and 24:1 for CX- and AC-rich foods, respectively. These conversion ratios are based on chemical structure, assuming that equivalent amounts of dietary AC-, BC-, and CX yield equivalent blood concentrations, and that these carotenoids have similar bioavailability. Objective: To associate concentrations of AC, BC, and CX in blood with their dietary intakes, thus comparing their bioavailability from food. Design: Dietary intakes were estimated by food frequency questionnaire (4 studies this laboratory, n = 116; ratios calculated for 8 other studies, n = 2340) or by food record (2 studies this laboratory, n = 59; ratios for 2 other studies, n = 118). Carotenoid concentrations were measured by reversed-phase HPLC. The ratio of dietary intake (d) to blood concentration (b) for AC, BC, and CX, was calculated, then ratios of ACb/d /BC b/d and CX b/d/BC b/d. Results: ACb/d/BCb/d was 1.5 (99% confidence 1.21-1.77), CXb/d/BCb/d was 15 (99% confidence 8.39 – 21.7). Thus, eating comparable amounts of AC-, CX and BC-rich foods would result in 1.5-fold greater AC and 15-fold greater plasma concentrations of CX plasma concentrations. Conclusions: This suggests that bioavailabilities of AC and especially CX from their main food sources are greater than that of BC, and thus AC and especially CX-rich foods might be better sources of VA than expected. The formation of VA from AC and CX deserves further study.