Flight speeds of Davy's naked-backed bat (Pteronotus davyi), Wagner's mustached bat (P. personatus), Parnell's mustached bat (P. parnellii), and Peter's leaf-chinned bat (Mormoops megalophylla) were studied in Colima, Mexico, during January 2000. Bats were assessed in a simulated cave passage cleared in a dense thorn forest. Rates of travel over a known distance were measured using stopwatches. Individual flight speeds varied from 7.4 (female P. davyi) to 30.6 km/h (male M. megalophylla); mean flight speeds ranged from 11.3 (male P. davyi) to 19.1 km/h (female P. parnellii). There was a positive correlation between mean forearm length and mean flight speed. Larger bats flew faster than smaller ones. Results of this investigation provide the first report of flight speed for female P. davyi (13.1 km/h) and extend our knowledge concerning the flight speeds of other taxa studied.