The stability constants of the complexes which were formed 3,4-diaminobenzenesulfonic acid (DAB) with nickel (II) and manganese (II) were determined potentionmetrically by using CALVIN-BJERRUM and IRWING-ROSSOTTI methods, in this work. The protonation constants of DAB were found as logβ1= 3.6 and logβ2= 4.0 at 20oC and I=0.1. according to the formation curves and the number of the stability constants the composition of complexes were determined as Metal/DAB=1/2. The stability constants of complexes were found logβ1=2.75 and logβ2=5.35 for nickel (II) complex and logβ1=3.65 and logβ2=6.89 for manganese (II) complex at 20oC. and I=0.1. The conditional formation constants and the formation pH ranges of complexes were determined as logK=5.30 and pH=0-12 for nicke (II) complex and log K=6.87 and pH=0-14 for manganese (II) complex. Keywords :