The study investigated patient- and program-level variables associated with attrition from intensive outpatient (IOP) substance use treatment in a national VA sample. National databases were used to identify a recent cohort of veterans receiving intensive IOP substance use treatment. Attrition was defined as receiving less than five visits of IOP treatment. Patient-level variables examined included age, gender, race, and psychiatric and medical comorbidities. Program-level variables examined included the number of hours of treatment offered, the percentage of patients living on-campus, and extent of staff cuts in the past year. Twenty-seven percent of veterans left treatment early. Being older, female, and having a psychotic disorder was associated with attrition. Program-level factors associated with attrition were the number of hours the program offered treatment, in that more treatment offered was associated with higher attrition. Focus on individual and program level factors associated with attrition is crucial to retaining individuals in treatment.