The present investigation aimed to compare fetal calf serum (FCS) and Tween 40 with the commonly employed tetrahydrofuran (THF) with respect to cytotoxicity, stability of the solubilized carotenoids, and uptake and accumulation of the xanthophylls astaxanthin (AX) and canthaxanthin (CX) in cultured human liver cells (HepG2). Incubation of HepG2 cells for 24 h with THF (C1.25%) or FCS (C11.25%) with or without AX (C25 lmol/L) or CX (C25 lmol/L) did not affect cell viability. Tween 40 (0.25-1.25% in medium) reduced cell viability by 75-99%. The stabilities of AX and CX in cell-free RPMI 1640 medium for B24 h were higher when delivered with THF instead of FCS. The doseand time-dependent accumulations of AX and CX (1-10 lmol/L) in HepG2 cells were higher when carotenoids were delivered with FCS compared to THF. In conclusion, FCS and THF, but not Tween 40, were suitable solvent systems for the delivery of AX and CX to HepG2 cells. In our experiments FCS was superior with regard to the uptake and accumulation of both carotenoids.