The movement patterns found in sandbathing were studied in selected species from all five genera of the rodent family Heteromyidae. The primitive subfamily Heteromyinae has a stereotyped pattern for spreading scent consisting of rubbing the ventrum on the substrate. There is no sandbathing in the functional sense. The Perognathinae and Dipodomyinae have both the ventral-rub and side-rub components and often combine these acts into a complex sandbathing pattern. These last two subfamilies have adapted to arid habitats and secrete copiously from their sebaceous glands. Evidence is given for the chemical communicatory nature of the places were sandbathing and ventral-rubbing have taken place. It is suggested that sandbathing has evolved secondarily as a pelage dressing motor pattern while still retaining a function as a means of chemical communication which is the only function of the simple ventral-rubbing found in the Heteromyinae. From a discussion of sandbathing in other rodent families it is proposed that the convergently-evolved sandbathing behavior has originated from different motor patterns.