Children with intellectual disability were randomly assigned to receive Milieu Communication Teaching (MCT) at one 1-hr session per week (low dose frequency, LDF) or five 1-hr sessions per week (high dose frequency, HDF) over 9 months (Fey, Yoder, Warren, & Bredin-Oja, 2013. Non-Down syndrome (NDS) and Down syndrome (DS) subgroups were matched on intelligence, mental age, and chronological age. The NDS group had significantly more growth in spoken vocabulary than the DS group. In the DS subgroup, the HDF group had more spoken vocabulary growth than the LDF group when IQ was controlled. In both etiological subgroups, the HDF group yielded greater vocabulary production outcomes than the LDF group for children who played functionally with a range of objects.