Kaplan memorial lecture. The family of human lymphotropic retroviruses called HTLV: HTLV-I in adult T-cell leukemia (ATL), HTLV-II in hairy cell leukemias, and HTLV-III in AIDS.

The past 5 years have witnessed the beginning of a new era in retrovirology, the era of human retroviruses. Within this short period the causes of two fatal human diseases have been defined as due to human retroviruses. In both instances in vitro systems have been developed which mimic the apparent in vivo effects of the viruses so that a reasonable amount of information on the involved molecular mechanisms has become available. The future promises much more such information, but what is much less certain is how soon will we learn to correct and/or prevent these diseases.