Technical Abstract: Estimates were made of broad sense heritabilities and the number of factors or genes involved in the production of total carotenoids and the major component carotenoids of carrot (Daucus carota L.) storage roots: phytoene, '-carotene, '-carotene, '-carotene, and lycopene. Two crosses with different backgrounds were evaluated: orange B493 x white QAL and orange Brasilia x dark orange HCM. The HCM (high carotene mass selection), Brasilia and B493 parents had both '-carotene and '-carotene, but HCM had proportionally more '-carotene. Carotene content in F2 populations ranged from 522 ppm to 1714 ppm in Brasilia x HCM and from 0 to 695 ppm in B493 x QAL progeny, and F2 plants segregating for absence of '-carotene were identified in B493 x QAL. Broad-sense heritabilities values for '-carotene, '-carotene, '-carotene and total carotenoid ranged from 28% to 48% and from 44% to 89% for lycopene and phytoene in the Brasilia x HCM cross, while all heritability values exceeded 88% for the B493 x QAL cross, except one estimate for lycopene. The estimated number of genetic factors conditioning '-carotene was 4, 2 to 3 each for '-carotene and total carotenes and one each for '-carotene, lycopene and phytoene in the orange x dark orange cross, and 4 factors for '-carotene, 1 to 2 each for lycopene and total carotenes and 1 for each of the other carotenes in the orange x white cross. These results are in general agreement with earlier QTL studies and they provided evidence for continuous inheritance of '-carotene, '-carotene and total carotenoids in the cross orange x dark orange and discrete inheritance for '-carotene and total carotenoids in the orange x white cross.