A novel class of carnitine derivatives is disclosed which comprises thiocarnitine and the S-acyl thiocarnitines wherein the acyl radical is the radical of saturated organic acids having from 2 to 10 carbon atoms. The S-acyl thiocarnitines are prepared e.g. by reacting crotonoyl betaine halogenide with the corresponding thio-acid, while thiocarnitine is obtained by hydrolysis of an S-acyl thiocarnitine. These compounds are useful therapeutic agents, e.g. for the treatment of intoxications, liver malfunctions and burns.