In this paper, a Hidden Markov Model (HMM) based speaker recognition system is presented. The system utilizes concatenated phoneme HMMs and works in a text-prompted mode. Each registered speaker has a separate set of HMMs which are trained using the Baum-Welch algorithm. The speaker recognition system has been evaluated with the YOHO voice verification corpus in terms of both speaker verification and closed-set speaker identification. It is shown that by using 10 seconds of testing speech, an error rate of 0.09% for male and 0.31% for female are obtained for speaker identification with a total population of 138 talkers. For speaker verification, under the 0% false rejection condition, the system achieves a false acceptance rate of 0.09% for male and 0% for female. This paper also explores effects of various factors (such as the mixture number and cohort selection) on the performance of speaker recognition.