A series of FITC-labeled hydrophobic molecules (1-8) were prepared, and their cellular uptakes have been investigated using cell-cycle-synchronized HeLa cells. The cellular membrane permeability of compounds strongly depended on both the chemical structure and the cell-cycle phase. In the G1/S phase, branched hydrocarbon-containing 3 and cis-olefin-containing 2 and 8 were efficiently internalized into cells by passive diffusion. In contrast, linear alkyl chain-containing 1 and 7 were retained on the membrane without rapid internalization. In the M phase, rapid permeation was suppressed for all molecules.