Lanosterol metabolism was elevated in yeast cells cultured both aerobically and semi-anaerobically by increased expression of lanosterol 14 alpha-demethylase P450 (P450(14DM) or CYP51). However, despite increases in the diene-intermediates of ergosterol biosynthesis, the ergosterol content was not affected. These results suggested that the levels of cellular sterols are controlled in at least two stages, and that the concomitant elevation of P450(14DM) and ergostadienols desaturase (P450(22DS)) is required to increase the cellular ergosterol content.