The effects of temperature, water activity ($a_{w}$), incubation time, and their combinations on radial growth and ochratoxin A (OTA) production of/by eight Aspergillus niger aggregate strains (six A. tubingensis and two A. niger) and four A. carbonarius isolated from Moroccan grapes were studied. Optimal conditions for the growth of most studied strains were shown to be at $25^{circ}C$ and 0.95 $a_{w}$. No growth was observed at $10^{circ}C$ regardless of the water activity and isolates. The optimal temperature for OTA production was in the range of $25^{circ}C{sim}30^{circ}C$ for A. carbonarius and $30^{circ}C{sim}37^{circ}C$ for A. niger aggregate. The optimal $a_{w}$ for toxin production was 0.95~0.99 for A. carbonarius and 0.90~0.95 for A. niger aggregate. Mean OTA concentration produced by all the isolates of A. niger aggregate tested at all sampling times shows that maximum amount of OTA (0.24 ${mu}g$/g) was produced at $37^{circ}C$ and 0.90 $a_{w}$. However, for A. carbonarius, mean maximum amounts of OTA (0.22 ${mu}g$/g) were observed at $25^{circ}C$ and 0.99 $a_{w}$. Analysis of variance showed that the effects of all single factors ($a_{w}$, isolate, temperature and incubation time) and their interactions on growth and OTA production were highly significant.