The Five Factor Obsessive Compulsive Inventory (FFOCI) was developed in part to facilitate a shift from the categorical classification of personality disorder to a dimensional trait model, more specifically, the five-factor model (FFM). Questions though have been raised as to whether obsessive–compulsive personality disorder (OCPD) can be understood as a maladaptive variant of FFM conscientiousness. The present study provides a further validation of the FFOCI, emphasizing in particular its association with FFM conscientiousness, as well as comparing alternative measures and models of OCPD. A total of 380 undergraduates (obtained in two samples of 274 and 106), including 146 oversampled for OCPD traits (93 for the first sample and 53 for the second), completed the FFOCI, measures of general personality, OCPD trait scales, and alternative measures of OCPD. Results supported the validity of the FFOCI as a measure of OCPD and maladaptive variants of FFM traits, as well as identifying substantive differences among the alternative measures of OCPD, particularly with respect to their relationship with FFM conscientiousness, antagonism, and introversion.