Two lizard communities, each consisting of seven residents plus several transient or immigrant species, were studied between 1970 and 1975 on a Chihuahuan desert watershed. Lizard species diversity was correlated with the previous 2 yr rainfall. H' varied between 1.28 and 1.91. The change in diversity in these lizard communities resulted from the influx of transient species and increase in numbers of resident species during a 2-yr wet period and the reverse during drought periods. The influx of transients and immigrants appeared to be related to the expansion of suitable habitat and the proximity to a source area for immigrants. The density of adult Cnemidophorus tigris nearly doubled in 1 yr which was attributed to above average overwinter survival of hatchlings. Seasonal activity periods of adults and hatchlings were longer during dry years than wet years. During wet years adults and juveniles of most species exhibited allochronic activity. Densities of most resident species varied directly with changes in productivity and relative abundance and activity of arthropods. Sceloporus magister numbers remained relatively constant over the 5 yr and this appeared to be related to availability of suitable habitat.