Abstract We studied the floristic composition and stand structure of lowland forests of the Maya Biosphere Reserve (MBR) of El Pete´ n Guatemala. Sampling was performed over a gradient of human influence including a newly established returnee community (migrant) the cooperative Unio´ n Maya Itza´ as well as an adjacent protected area within the core area of the MBR. Five 1-ha plots each divided into 100 contiguous 10 9 10 m2 subplots were used to record presence of all tree and vine species. The study area is a low-diversity rainforest with a canopy layer dominated by species of Fabaceae a shrub layer dominated by Rubiaceae and vines dominated by Bignoniaceae. Vines were conspicuous both in number and in diversity. Variation in both tree life-form composition and canopy abundance pattern apparently reflect variation in intensity of forestry among the plots. The similarities between the plots in the cooperative (a logging plot and a settlement plot) with regard to species area curves and mean number of tree and understory species per subplot may indicate effects of disturbance (in general) on vegetation structure. Detrended correspondence analysis (DCA) was used to investigate gradients in species composition among the five plots (125 subplots) and to generate hypotheses about vegetation–environment relationships. The study area appears as a mosaic of site-specific forest types or associations determined by a particular species or groups of co-dominant species. The main environmental characteristics of the area determining species composition and structure are related to the drainage of soils and human disturbance.