Inventory sampling provides information on assemblage structure and baseline species diversity data for future comparisons. This study explored the efficiency and accuracy of inventory sampling methods for an assemblage of lowland tropical amphibians and reptiles. Data were collected from the Iwokrama International Centre for Rain Forest Conservation and Development in Guyana. Four standard methods (day visual encounter survey, night visual encounter survey, leaf litter plots, and opportunistic collecting) were used to examine assemblage structure. I analyzed these data to look for variation in amphibian and reptile species diversity among different parts of the reserve and different methods. Species diversity varied among the different populations sampled in terms o f species richness. Estimations in species richness also varied among methods. Night visual encounter surveys provided the highest average number of individuals and species caught per person-hour of effort. However, a combination of methods portrayed the most accurate species richness within the reserve.