The purpose of this paper is to compare structured input (SI) with other input-based instructional treatments. The input-based instructional types include: input flood (IF), text enhancement (TE), SI activities, and focused input (FI; SI without implicit negative feedback). Participants included 145 adult learners enrolled in an intermediate Spanish course. Learners completed a pretest, treatment, immediate posttest, delayed post-test (three weeks after treatment) and an extended delayed post-test (six weeks after treatment) measuring both interpretation and production of the Spanish accusative clitics. The results revealed significant findings for all groups on the interpretation task, with SI being the most robust. The findings for the production measures are not so straightforward; however, all groups showed some improvement. The theoretical and methodological ramifications of these findings are discussed.