The solvent extraction of zinc(II) and cadmium(II) from sulfate medium by 1 - phenyl - 3 - methyl - 4 - benzoylpyrazol - 5 - one (HPMBP) was studied in the following parameter functions: pH, concentration of the extractant, nature of diluent, concentration of the mineral anion and synergism. In the absence of the synergic agent methyl - isobutyl ketone (MIBK), the complexes extracted are $ZnL_2(H_2O)_x(org)$ and $CdL_2(H_2O)_y(org)$ . In the presence of MIBK, the curves of extraction show the presence of several species of complexes that depend on the concentration of MIBK. For very weak concentrations, the extracted complexes are $ZnL_2(H_2O)_x (org)$ and $CdL_2(H_2O)_y (org)$. For high concentrations, the extracted complexes are $ML_2(MIBK)_(org)$ , $ML_2(MIBK)$,$MIBK_(org)$ and $ML_2(MIBK)$,$2MIBK_(org)$ (M=Zn, Cd). The extraction constants were calculated.