The effects of gas‐oil, fuel‐oil 2,4‐dinitrophenol and hexadecane, the latter either in injection or applied to the skin of mice have been studied in applications scheduled every 12,24 or 48 hours. Studied were effects upon body weight and on the lipid and protein levels of liver and muscle as well as on plasma composition of mice. The effects of all materials tested were very similar, inducing a biphasic effect on body weight: increases with low doses/delayed applications and decreases with high doses/frequent applications. This is tentatively explained as an impairment of the hydric balance as well as effects on thermogenesis through brown adipose tissue oxydative phosphorylation uncoupling elicited by hexadecane. The 3 week treatment with hexadecane resulted in a maintenance of circulating glucose with increases in urea, amino acids and lactate, as well as losses of liver lipids in all groups treated with alkanes or 2,4‐dinitrophenol. The results agree with powerful and lasting effects of hexadecane on...