The Commitment Inventory measures interpersonal commitment (dedication) and constraint commitment. Since it was first published, substantial revisions have been made, but there are no published data on the psychometric properties of the new version. Furthermore, little information is available on measuring commitment for unmarried couples. This study examined the psychometric properties of the Commitment Inventory in 320 premarital or cohabiting couples (N = 640). Dyadic confirmatory factor analyses revealed that the hypothesized factor structure of six constraint subscales and one dedication subscale fit the data well for both men and women. Internal consistency coefficients were within acceptable range for most subscales. Within-couple correlations as well as correlations between subscales and with relationship quality, negative communication, and religiosity are presented. Implications for future research are discussed. (Contains 5 tables and 2 notes.)