An anger therapy intervention was developed for incarcerated adult males. The therapy was an extension of cognitive-behavioral approaches, incorporating principles and practices drawn from Buddhist psychology. Adult males from a Midwestern low-security prison were randomly assigned to either a treatment group (n= 16) or a waiting list control group (n= 15). Following a 10-session intervention, treated participants exhibited significant reduction in anger relative to those in the control group. Greater reductions in anger for the therapy group was mediated (p = 0.07), by greater reduction in egotism relative to the control group. Contrary to predictions, anger reduction was not mediated by increases in empathy. Implications for designing and delivering interventions in prison settings are discussed. (Contains 1 figure and 1 table.)