For a study, the researchers determined expressive language sampling (ELS) as a procedure for generating spoken language outcome measures for treatment research in Down syndrome (DS). Participants were 107 individuals with DS between 6 and 23 years of age who presented with intellectual disability (IQ<70). Low rates of noncompliance were observed; youth under 12 years of age, had phrase-level speech or less, and had a 4-year-old developmental level or less were at particular risk for experiencing difficulty completing the ELS procedures. Minimal practice effects and strong test-retest reliability across the 4-week test-retest interval were observed. The vocabulary, syntax, and speech intelligibility variables demonstrated strong convergent and discriminant validity. Although significant correlations were found between the variables derived from the conversation and narration contexts, some differences were noted. The ELS procedures considered were feasible and yielded variables with good psychometric properties for most individuals with DS between 6 and 23 years old. The research measured appropriate for individuals with DS with more limited spoken language skills were needed. Context differences observed in ELS variables suggested that comprehensive evaluation of expressive language was likely best obtained when utilizing both contexts.