Purpose-The goals of this investigation were to determine whether gains in the use of tense and agreement morphemes by children with specific language impairment (SLI) during a 96-session intervention period would still be evident one month following treatment, and whether these treatment effects would be greater than those seen in children with SLI receiving otherwise similar treatment that did not emphasize tense and agreement morphemes.Method-Thirty-three children with SLI (age 3;0 to 4;8) served as participants. The children participated in one of three treatment conditions. The conditions emphasized third person singular -s, auxiliary is/are/was, or general language stimulation. The children's use of third person singular -s, auxiliary is/are/was, and past tense -ed was assessed through probes administered throughout treatment, and one month later.Results-The children in the conditions that targeted third person singular -s and auxiliary is/ are/was showed significant gains on their respective target morphemes and these gains were maintained one month later. These gains were significantly greater than the gains seen on the same morphemes by the children receiving general language stimulation. For most children, use of the target morphemes did not approach mastery levels by the end of the study.Conclusions-Intervention that emphasizes morphemes that mark both tense and agreement can be relatively successful, with gains still apparent at least one month following intervention.This report presents data from the third phase of a research project on the acquisition of tense and agreement morphemes by children with specific language impairment (SLI) during intervention. The first two phases were presented in this Journal by Leonard, Camarata, Brown, and Camarata (2004) and Leonard, Camarata, Pawłowska, Brown, and Camarata (2006).In the previous studies (Leonard et al., 2004;Leonard et al., 2006), children with SLI aged 3 to 4 years participated in one of two treatment conditions. One condition focused on the target morpheme third person singular -s; the other condition centered on the target morphemes auxiliary is/are/was. (Hereafter, children assigned to these conditions are referred to as the 3S and AUX children, respectively.) All of the children showed limited or no use of these morphemes prior to treatment. Other developmentally appropriate morphemes used rarely if at all by the children were also monitored during this period, but NIH Public Access