Deregulation of the cable industry has been based largely on the assumption of existing diversity and competition and on the promise of promoting diversity within the industry. To test this assumption, a study examined levels of channel diversity for a sample of cable systems at three stages of the deregulation process. A random sample of 326 fully operational cable systems was selected and a typology of 32 different types of programming available to cable operators were defined and differentiated. Information was then collected on the capacity and size of each system, and the program channels offered by the system at three subsequent points in time, corresponding to periods of high (1976), moderate (1981), and no regulation (1986). Results indicated that the level of diversity in cable programming has increased since the restrictive policy era of the early 1970s, but findings question whether cable has truly lived up to its potential for diversity. (Two tables of data are included; 19 references, a chronology of selected cable regulation/deregulation, and the typology of channel diversity are attached.) (RS)