Two series of pyrimidine derivatives (pyrimethanil and N-acetyl pyrimethanil) were tested to show their effect on the metabolic activity of Aspergillus niger.  The two compounds have been used with different concentrations of 0, 2.5, 5 and 10 µg/ml to indicate the fungus ability to produce cellulase, Endo 1,4B glucanase and chitinase enzymes. The highest levels of Endo 1,4B glucanase and cellulase enzymes production were at concentration of 2.5 µg/ml of pyrimethanil compound and 10 µg/ ml of N-acetyl pyrimethanil compound. On the other hand, there is no production of chitinase enzyme by A. niger was recorded either on the presence or absence of any concentrations of the two compounds. When examining the effect of the two compounds on lytic enzymes production by A. niger, the results showed that the concentration of 5 µg/ml and 10 µg/ml of pyrimethanil compound led to increases in enzymes production and their activities on living and killed cells of E. coli and B. subtilis, respectively. Also by using the N-acetyl pyrimethanil compound with concentrations of 2.5 µg/ml and 10 µg/ml, led to an increase in the activity of lytic enzymes on living and killed cells of both E. coli and B. subtilis, respectively. While those lytic enzymes weren't showed, in the presence or absence of the two compounds, any lytic activity on living and killed cells of A. niger. Addition of 2.5 µg/ml of pyrimethanil compound and concentration of 10 µg/ml of N-acetyl pyrimethanil compound, increased the extracellular protein production by A. niger.