We examined plant climbing by the common striped scorpion Centruroides vittatus to determine which of two hypotheses (the predation avoidance hypothesis or the increased prey availability hypothesis) best explained this behavior. In the field we observed nocturnal scorpion activity for 16 mo during 1992–1993 to quantify climbing behavior and collected data on potential prey abundance on the ground and in vegetation for 5 mo. We also performed a laboratory experiment examining the effects of hunger level on scorpion climbing and activity. Individuals found up in vegetation accounted for 19.3% and 25.2% of scorpions active in 1992 and 1993, respectively. Juveniles were significantly more likely to be found in vegetation than were adults in both years, although juveniles and adults did not differ in the proportion found carrying prey in vegetation. We found significant seasonal variation in prey abundance, with prey density being greatest in September. Prey density was also significantly greater on the ground than in vegetation when all trapped invertebrates were included; however, when we excluded collembolans because of their small size, this difference was no longer significant. Laboratory results indicated that there were no within-treatment differences among age classes/sexes in any behavior (climbing frequency, activity level or maximum height climbed). When hungry, males (but not females or juveniles) climbed higher and juveniles (but not adults) were more active. Hunger level had no effect on climbing frequency for any age class/sex. In combination, the field and laboratory data are most consistent with the predation avoidance hypothesis as the main reason for plant climbing by scorpions.