This study assessed agreement level about the occurrence of past-year male-to-female partner violence (MFPV) and female-to-male partner violence (FMPV) among a sample of 897 blue-collar couples. Intimate partner violence (IPV) was measured with the Physical Assault subscale of the revised Conflict Tactics Scales (CTS2). Agreement level was assessed with Cohen's kappa statistic. Lower-bound estimates (based on couple agreement that an IPV event occurred) and upper-bound estimates (based on uncorroborated reports from either partner that an IPV event occurred) were calculated. Results indicated low agreement for most IPV behaviors ([kappa] less than 0.40). Estimated lower- and upper-bound rates for MFPV were 6.7% and 21.2%, for FMPV, 7.1% and 24.2%, and for any IPV, 10.1% and 30.2%. Findings suggest that single-point IPV prevalence estimates are biased; lower- and upper-bound estimates using collateral reports should be calculated when possible. In addition, findings underscore the importance of conducting IPV research among understudied populations, such as working-class couples, that may be at elevated IPV risk. (Contains 3 tables.)