Historically, much attention has been given to the multifaceted problems experienced by drug abusers. Recently, greater attention has been given to the family members of drug abusers, but unfortunately, most of this attention has focused on family relationships and has overlooked the problems experienced by family members of drug users (DUs). To date, there is no psychometrically sound, multidimensional assessment tool available to systematically assess the economic, behavioral, and psychological problems encountered by these family members. This study presents the findings associated with the initial measurement development phase of such an assessment tool. The initial results are promising, suggesting that the Significant Other Checklist (a) has reasonable initial subscale reliability estimates, (b) assesses problem domains that are relevant to family members of DUs, and (c) is able to identify important group similarities and differences among family members of DUs.