• To examine the efficacy of rehearsal in reducing distress in 3- to 6-year-old children undergoing diagnostic cardiac catheterization, 40 children were assigned randomly to the rehearsal preparation procedure or to usual preparation. The rehearsal program involved the use of behavioral rehearsal in the catheterization laboratory, manuals to explain the procedure to the parents, and coloring books to provide parents and children with a vicarious experience of catheterization. Rehearsed patients cried, yelled for mother, complained of pain less, and showed lower rates of motor activity than did control patients. Rehearsed patients also showed less overt regressive, aggressive, and anxiety behaviors at home following the catheterization than did controls. Parents in the rehearsed group showed less anxiety following the catheterization, and negative reactions in children correlated significantly with parental anxiety. Participants' reactions were uniformly more positive in the rehearsed than in the control patients.