Seventy-four (74) bacterial isolates from various soils and vegetation types in Trinidad and Tobago were identified as nitrogen fixers. Morphological and physiological characteristics indicated that the isolates belonged mainly to the genera Azotobacter, Clostridium, Bacillus and Beijerinkia. Others that could not be more clearly identified appeared to be of the Bacillaceae and Enterobacteriaceae families. None of the isolates were identified as Spirillum species although there was presumptive evidence of their presence. There were more isolates and greater physiological diversity among the isolates from rhizosphere compared with nonrhizosphere soils.