Transpiration by riparian trees in the Okavango Delta (Botswana) creates a salinity gradient which facilitates continuous water movement from the swamps to the islands. This leads to salt accumulations underneath islands which minimizes surface water salinity. The aim of this study was to investigate spatial variation in population size structure of riparian tree species in the Delta. It was hypothesized that riparian tree population structure will vary spatially due to different hydrological conditions. Riparian vegetation was surveyed in Boro, Santawani, Moremi, Vumbura and Seronga from a total of 75 plots measuring 20m x 50m. Species chosen for this study in terms of their dominance were Croton megalobotrys Müll. Arg, Philenoptera violacea (Klotzsch) Schrire, Diospyros mespiliformis Hochst. Ex A.DC and Acacia nigrescens Oliv.. Diameter at breast height (dbh) was measured for tree individuals with stem diameter >2.5cm. Linear regression analysis was used to infer population size class distribution of each species. Croton megalobotrys Müll. Arg showed a reverse J size class distribution (SCD) pattern in Boro, Santawani and Vumbura while it showed a bell shaped pattern in Moremi. Philenoptera violacea (Klotzsch) Schrire showed an irregular size class distribution pattern with some missing size classes in Boro and Santawani while it showed a reversed J shaped size class distribution pattern with more individuals in the lower size classes in Vumbura. Diospyros mespiliformis Hochst. Ex A.DC showed a U shaped SCD pattern in Boro and irregular pattern in Seronga and Vumbura. Acacia nigrescens Oliv. showed irregular SCD pattern with some missing size classes in Boro and Santawani and reverse J shaped SCD pattern with more individuals in the lower size classes in Seronga. Keywords: Diameter at breast hight (dbh), Okavango, Recruitment, size class distribution (SCD), Species.