A new liquid-membrane electrode incorporating Mn(III)-porphyrin and Zn(II)-dipyrromethene has been studied for direct salicylic acid determination in human plasma. The membranes were doped additionally with lipophilic salts of tetrakis(p-chlorophenyl) borate (KTpClPB) or tridodecylomethylammonium chloride (TDDMACl) in order to improve the sensitivity and selectivity of the ISEs studied. Both types of the ISEs display good sensitivity, very short response time, and lack of interference from the major components of human plasma. The contents of salicylate in the samples of natural human plasma were determined by a potentiometric method using the electrode proposed. The results obtained were in good agreement with those obtained by the Trinder spectrophotometry method. The ISEs incorporating Mn(III)-porphyrin and Zn(II)-dipyrromethene are suitable for the direct determination of salicylate in human plasma.