This paper examines input and negotiation in child and adolescent second language acquisition. Two hypotheses are tested: first that adult native speakers provide more simplified input to younger learners than to older learners; and second. that older learners use more conversational negotiation devices and techniques than younger learners. To test these hypotheses fourteen Spanish speakers oust beginning to acquire English). seven children and seven adolescents were paired with fourteen adult native English speakers in such a way that fourteen conversational dyads were formed lo provide baseline data an additional fourteen native English speakers were matched with each other. Each dyad was asked to participate in a block-building task Conversations during these tasks were audiotaped, transcribed and analyzed. The analysis provides evidence which is consistent with the two research hypotheses presented above.