The physical chemical properties, stability and incompatibility of captopril (the active ingredient of Tensiomin tablets) have been discussed. Captopril has two polimorphic crystal modifications, the form I. of higher melting point is applied in the therapy. Captopril has a better stability in solutions below pH 4, the degradation is accelerated by metallic ions (Cu, Fe). In solid phase the degradation is accelerated by the humidity of the air. No incompatibility was found with the tabletting excipients but stearic acid and sodium-carboxymethyl-starch. Under compaction at higher pressure captopril itself shows tendency for lamination. The dissolution rate of the Tensiomin tablets can meet the requirement of USP if direct tabletting method was used. In this case the breaking strength of the tablets has no influence on the dissolution rate. The main properties (weight uniformity, content uniformity, tensile strength, friability, disintegration time, dissolution time) of the Tensiomin tablets of 12.5 mg, 25 mg, 50 mg and 100 mg of captopril meet the requirement of USP not only after manufacturing but after the accelerated stability test of three month as well.