Baited pitfall traps were used in Barclay Cave, Alabama, in 1965 to study a blind Ptomaphagus beetle population. A 40m2 area in the cave yielded 95% of the 897 adult and larval beetles trapped in the cave at 9 stations. This represented a population density of about 13 beetles/m2. Tests of different baits showed decayed meat to be the most attractive. Adults were most abundant in mid-August when substrate conditions were moist, were reproductively active, and were not newly emerged from pupal cells. Larvae were most abundant in late August. The population was studied by mark-recapture methods for 8 years after the pitfall trapping, and it was judged to have recovered to former densities after about 6 to 8 years. The use of traps which kill cave invertebrates is not encouraged for most future cave ecology studies. Population densities of beetles at baits in Cold Spring Cave were found to be 139 adults/m2 in 1968, and to much lower in three later years.