The utility of radiotelemetry as a tool for estimating the size and microhabitat requirements of a population of Lacerta lepida, the largest European lacertid, was investigated in central Spain. Population density estimates based on repeated marking and recapture (3.2 lizards ha−1) were much higher than those based on line transects (0.22 lizards ha−1). The probability of sighting lizards before they could retreat into a refuge was largely increased by our ability to radiolocate them. Rocks were selected as refuges 96% of the times, and the locations of radiotracked lizards were much closer to rocks than randomly expected. Rocks used as retreat sites were larger and had more crevices than those available at random, which suggests that refuge selection was primarily determined by the need to find shelter from predators. Rockrose patches, which were positively selected, might be used as refuge-connecting corridors that combine shelter with opportunities to forage and thermoregulate. Our results emphasize the need for using radiotelemetry to establish baseline information on abundance and to clarify the actuality, extent and pattern of the population declines experienced by species that may function as key links in their ecosystems, but the wariness of which poses a serious problem for monitoring their conservation status.