The Megargee and Dorhout classification system rules were applied to 181 MMPI profiles from inmates at a level 4 Federal Correctional Institution in Memphis, Tenn. Unambiguous classification was easily obtained for 92 percent of the inmates. The dispersion of these inmates among the 10 Megargee types was comparable to that previously reported at other levels of the Federal prison system. A total of 50 of these inmates were retested after a mean test interval of 10.16 months. Only 14 of these 50 inmates retained their original type designation upon retesting. Although the Megargee and Dorhout typology may be easily applied to inmate MMPI profiles in an institution at this level, the marked instability of the system suggests that considerable caution should be excerised if it is to be used in the classification process. Six references are included.