Response of rice to root inoculation with Azospirillum under different N fertility levels was studied over three consecutive seasons under tropical conditions. The response to Azospirillum was more pronounced at lower levels (30 and 45 kg N/ha) of fertilizer N than at a higher level (60 kg N/ha). Although the root inoculation with Azospirillum resulted in a significant increase in mean yields of both grain and straw especially at low levels of N (30 and 45 kg N/ha), the interaction between the N fertilizer and inoculation was not statistically significant.