Recent investigations have supported the ability of persons with Down syndrome to continue learning language on into adulthood. The importance of intervention to increase communicative competence is evident--what is not known is the effectiveness of such intervention. The authors report here on a series of case studies that investigated a language intervention that targeted syntax for adults with Down syndrome. The intervention used a hybrid approach combining naturalistic intervention contexts with structured elicitations of targets. Three adults with Down syndrome, ranging in age from 29 to 52 years, participated in 12 treatment sessions targeting grammatical morphemes. Results indicated that all three participants increased their use of target structures in obligatory contexts.