This paper describes the spatial and temporal distribution of Anopheles gambiae s.l. Giles in two Tanzanian villages based on data collected from a five-month intensive mosquito sampling programme and analysed using Taylor's power law. The degree of spatial aggregation of female A. gambiae in each village was similar to its corresponding temporal aggregation, indicating that in designing sampling routines for estimating the abundance of mosquitoes, sampling effort should be allocated equally to houses (spatial) and nights (temporal). The analysis also showed that for a given amount of sampling effort, estimates of village-level mosquito abundance are more precise when sampling is carried out in randomly selected houses, than when the same houses are used on each sampling occasion. Also, the precision of estimating parous rates does not depend on whether mosquito sampling is carried out in the same or a random selection of houses. The implications of these findings for designing sampling routines for entomological evaluation of vector control trials are discussed.