Abstract Psychosocial constructs have been used to predict colorectal cancer screening and are frequently targeted as intermediate outcomes in behavioral intervention studies. Few studies have conducted analyses to adequately test construct validity. The psychometric analyses undertaken with U.S. populations of 16 theory-based, colorectal cancer screening items designed to measure five factors (salience-coherence, cancer worries, perceived susceptibility, response efficacy, and social influence) are an exception. The current investigation replicates previous work by examining factor validity and invariance in a random sample of Ontario, Canada residents. A survey instrument was administered to 1,013 Ontario male (49%) and female (51%) residents randomly selected by the Canada Survey Sample. Single-group confirmatory factor analyses (CFA) assessed data fit to the proposed five-factor model for males and females separately, and then a multigroup CFA evaluated if the factor structure was invariant for men and women. The five-factor model provided good fit for both males and females. Tests for factorial invariance between sexes, however, found mixed results. χ2 difference test was significant (P = 0.025); however, ΔRMSEA = 0.0001. Factor loadings were similar by sex except for two social influence items, with item frequency distributions suggesting an extreme response style, in females, on these items. Overall, the single-group and multigroup CFA results support factorial validity and partial invariance of the five-factor model first identified in the U.S. populations. The items can be used to evaluate and compare psychosocial correlates across U.S. and Canadian samples. Additional research is needed to show invariance for other ethnocultural and national subgroups. (Cancer Epidemiol Biomarkers Prev 2008;17(11):3279–83)