The subjects had never served a sentence in a Federal penitentiary, and their sentences ranged from 2 years to life. Self-concept was measured by the Twenty Statement Test (TST) which asks subjects to give 20 answers to the question 'Who am I?' Self-esteem was measured by asking subjects to evaluate each particular characteristic they had indicated on the TST. Each subject was tested on three occasions: at the provincial correctional center where sentenced inmates are held until transfer to prison, after admittance processing at the Federal penitentiary, and 8 weeks after admittance. Self-conception over the three interview waves was not stable for three-fourths of the subjects. The greatest change in self-conception occurred not in the initial shock period, but between stages two and three when the subject had been in the general prison population for a month. Analysis revealed a steady increase in self-esteem over the testing period. Finally, the scope of self began to stabilize within 4 weeks of admittance to the prison, and this self was maintained as the subject moved along his prison career. Charts and six references are included.