Diurnal drop-off rhythms were exhibited by all three stages of Rhipicephalus appendiculatus engorging on cattle in stalls under natural conditions of light and temperature. Most engorged larvae dropped from the host between 1000 and 1400 hours, most nymphs between 1200 and 1800 hours, and most adults between 0600 and 0800 hours. Under controlled conditions of light and temperature the drop-off rhythms of larvae and nymphs engorging on rabbits were synchronized by oscillators set in the tick in the pre- and postattachment periods. The possibility of a host-induced rhythm was inferred from the data. Drop-off patterns may be used to enhance tick control methods.