A reversed-phase ion-pair high-performance liquid chromatografic method (RP-IPC) was developed to assay some water-soluble vitamins in solution dosage forms. Vitamins of the B-group B 1, B 2, B 3, and B 6, including vitamin C were determined in Oligovit ® coated tablets. In Beviplex ® coated tablets the vitamins B 1, B 2, B 3, B 6 and p-aminobenzoic acid were analysed. Hexanesulphonic acid sodium salt and triethanolamine in water–methanol were used as mobile phase with adjusting pH to 2.8 with orthophosphoric acid. Phenol was used as an internal standard. For quantitative simultaneous analysis of vitamins in pharmaceutical formulations, the method of internal standard was used. All parameters for the validation of the method are given.