Silylation of salicylic acid by hexamethyldisilazane, N,O-bis(trimethylsilyl)acetamide, and N,N-bis(trimethylsilyl)trifluoroacetamide was compared using GLC. The completeness of the reaction, the stability of products, and the reproducibility of results with time were investigated. Different reaction vessels were examined for their reliability and application for a routine assay procedure.