Eight commercial methamphetamine test kits : AbuSign, accuPINCH,AccuSign, I.D. BLOCK, Medi-Mate, QuikPac II, SureStep and Visualine E were evaluated for their interferences by twelve drugs commonly found in over-the-counter cold syrups: aspirin， brompheniramine, chlorpheniramine, ephedrine, etheraamide, guaifenesin, Nphenylephrine， methylephedrine, pheniramine, phentermine, phenylpropanolamine, and pseudoephedrine; and by clobenzorex, ranitidine which have been found to interfer in some amphetamine Immunoassays. These fourteen drugs were evaluated by using measured concentrations ranging from 1 mg/L to 1000 mg/L. Results indicate that ephedrine and pseudoephedrine demonstrate a significant interference in most of test kits, while most analgesics, antihistamines and antitussives show no interference with the exception of brompheniramine.