A gas chromatography-mass spectrometry method is described for the identification and quantitation of 6-hydroxy-1,2,3,4-tetrahydro-beta-carbohne (60HTHBC). During the analysis of 60HTHBC in human platelets, the artifactual formation of 60HTHBC was observed and shown to be due to the presence of formaldehyde in both organic solvents and in platelet homogenates. Formaldehyde was facilely removed from the organic solvent via a Pictet-Spengler reaction; however, removal from tissue homogenates was not possible by using conventional aldehydetrapping agents. The solution of these problems and their consequences for persons attempting to establish the in vivo presence of tetrahydro-beta-carbolines or biochemically study tissue preparations are discussed.