The composition and purity of three commercial preparations of the widely used affinity chromatography ligand Cibacron Blue F3GA have been evaluated by TLC and by paired-ion reversed-phase HPLC and were found to contain several chromophoric species. Stepwise synthesis of the reported dye structure showed that only one commercial preparation contained any actual Cibacron Blue F3GA, and that it was present only in minor amounts. In all three preparations the major component appears to be the dichlorotriazinyl precursor of Cibacron Blue F3GA. Commercial samples of the related dyes Procion Blue MX-3G and Procion Blue MX-R are also highly heterogeneous. In addition, our experiments suggest that TLC results must be evaluated carefully to ensure that catalytic surface activity of alumina and silica has not created ghost bands.