In the 1960's and early 1970's, prison administrators sought to determine the causes of the increasing prison unrest. Some corrections officials argued that the indeterminate sentence was a major factor in prisoner discontent and misbehavior. Other prison administrators believed that a move toward determinate sentencing would increase prisoner misconduct, because prisoners would be less motivated to participate in prison programs and above institutional rules. To date, this debate has lacked empirical evidence. This article remedies this by analyzing prison rule violations in California and Oregon, two States that recently enacted determinate sentencing laws. Data on the number and types of prison rule violations were obtained before and after 1977, the year both determinate sentencing statutes went into effect. During 1978 and 1979, numerous interviews were also conducted with prison administrators at four of California's 12 main correctional institutions and all three of Oregon's prisons. The data indicate that prisoner misconduct is not directly associated with the transition from an indeterminate to a determinate sentencing system. To understand the complex nature and causes of prisoner misconduct more fully, prison officials and researchers must examine a variety of other factors, including prison overcrowding, racial tensions, the declining median age of inmates, gang activities, and the variation in forms of prison administration. Tabular data and 13 bibliographic listings are provided.