This study assessed effectiveness of simultaneous prompting procedure in teaching two middle school students with cognitive impairment decimal subtraction using regrouping. A multiple baseline, multiple probe design replicated across subjects successfully taught two students with cognitive impairment at middle school level decimal subtraction involving double digits and to hundredths place. Data collected over a period of approximately three and a half months indicated maintenance and generalization of the skill learned across materials, settings, and people. Experimental control was validated when student responses increased in accuracy only after the intervention was implemented with each student. (Contains 2 figures and 3 tables.)