The taxonomic composition and functional feeding groups (FFG) of macroinvertebrate communities were characterized along a stream-size gradient of four streams in Trinidad, two being impacted by agricultural and urban activities (Arima and Guanapo Rivers) and two being relatively pristine (Marianne and Paria Rivers). The degree to which benthic assemblages have been altered by agriculture and input of treated domestic waste was assessed, by comparing the longitudinal patterns between the north-flowing (unimpacted) and south-flowing (impacted) streams. Both univariate and multivariate analyses indicated significant changes in macroinvertebrate community function, with smaller changes in taxonomic composition, along the gradient. Such changes were less conspicuous in the north-flowing than the south-flowing streams. This study indicates that land-use can have more of an influence on the macroinvertebrate community than the natural longitudinal gradient.