Countertransference reactions can either benefit or hinder mental health professionals during the therapeutic process. An awareness of countertransference reactions can aid clinicians in understanding and anticipating their own specific emotional responses toward certain client populations. Recent empirical research suggests that common countertransference reactions may occur in mental health professionals when relating to certain client types. Since a literature review indicated that more numerous and reliable tests have been developed to measure countertransference during the past decade, as well as better research designs, this article reviews and summarizes all empirical research studies on countertransference reactions toward specific client populations during the past 10 years, from 1990 to 2001.