This study compares self-reports by a sample of 50 opiate addicts with reports of 50“significant other”informants, on past and current functioning. Moderate to high levels of agreement are found using the Intraclass Correlation Coefficient (ICC) in reporting current opiate use, current employment, and current legal pressures. This finding is consistent with previous studies which found good agreement between addicts and informants in these areas. However, much poorer agreement between addicts and informants is found in assessing the severity of addict's social, employment, and psychological problems, and in assessing the more detailed aspects of drug use. A comparison of the percent agreement data with ICC data used in this study provides empirical support for the argument that percent agreement data represents an inflated estimate of concordance between raters. These findings suggest that addicts and their families have rather divergent perceptions of the addict's problems and, in addition, indicate the value of including family members or significant others in the process of evaluating and treating opiate addicts. The results of the statistical analysis underscore the need in reliability studies of rigorous statistics that take into account chance agreement.