Impulsive sensation seeking, an important index of the disinhibited pursuit of novelty with minimal concern for potential negative consequences, varies with important health behaviors like drug use and unsafe sex. Previous work reveals associations between impulsive sensation seeking and gender, age, ethnicity and education. Links to these sociodemographic variables should arise from actual differences in the trait and not potential biases in items on the scale. The current study employed item response theory (IRT) analyses to identify differential item functioning (DIF)—a variation in scores that arises from group membership that is independent of genuine differences on the trait. Analyses of data from a large sample of Internet responders revealed DIF on multiple items of a popular index of impulsive sensation seeking. Items showed DIF in analyses related to gender, age, ethnicity and education. These results suggest that sociodemographic differences in impulsive sensation seeking should be interpreted with caution as they may be due to idiosyncratic interpretation of items rather than true group differences on the underlying trait. Future research should explore how these biases might affect links between impulsive sensation seeking and related psychological and behavioral outcomes.