A selective, sensitive, rapid and well reproducible TLC-densitometric method has been developed for simultaneous determination of sulphonamides (sulfamethoxazol, sulfadoxin, sulfamerazin, sulfametrol, sulfadiazin) in combination with trimethoprim in various dosage forms. The R. S. D. (%) is 1.09 to 1.82 for the sulphonamides and 1.1 for trimethoprim. The method is suitable not only for quantitative evaluation of sulphonamides and trimethoprim in all commercial drug forms (tablets, injections, suspensions, syrups, pulvis), but also for checking the identity of the active substances.