Abstract The isolation, detection and identification of twelve alkaloids or alkaloid-like substances from aqueous solutions are described. The best extraction was obtained with chloroform, and the detection and identification was performed by thin-layer chromatography. These extraction and chromatography procedures were applied to the isolation and detection of the same alkaloids from biological materials after their injection and passage through the bodies of horses. Samples of saliva, plasma and urine were examined at different times after the injection. Urine seemed to be the most reliable biological fluid for the detection of these substances. The method fully satisfies the requirements for the rapid determination of these substances in doped race horses and even in human athletes.