The study found little difference between the treatment outcomes experienced by respondents and nonrespondents in an evaluation of an adolescent substance abuse treatment program. This finding pertained to a large number of attributes known to be associated with recovery and relapse in adolescents treated for substance abuse. The followup telephone survey was successful in contacting 53 adolescents, but was unable to contact 61 adolescents ("nonrespondents"). This study suggests that nonresponse in followup evaluations does not introduce significant bias in outcome data. Study subjects were 114 adolescents discharged from a primary substance abuse treatment facility in the Midwest. The treatment facility discharges adolescents if they have met all of their treatment goals, which include maintaining abstinence from drugs and alcohol during treatment along with other behavioral goals. Followup data were obtained from telephone interviews with discharged adolescents conducted annually by the facility. Followup data are collected with a 230-item questionnaire that contains questions in several domains believed to be related to treatment success. This study compared the information contained in the treatment records of the adolescents who responded to the survey with those who, for one reason or another, could not be contacted. 3 tables and 17 references