Prisoners' rights have not emerged de novo like all rights, but rather are embedded in a history dating back at least to the Magna Carta. More recently, they have been shaped by post-Civil War amendments and legislation and by 20th century legislation and case law. Data from national trends and filings by Illinois inmates for 1977-1986 indicate that the relatively few inmates who litigate have created a significant body of case law. Inmates primarily sue to transform confinement conditions rather than to obtain release. Their efforts have resulted in some form of relief, indicating that law can be effective in curbing the most serious abuses of state power. The most obvious change have occurred in the judiciary and in prison administration. 3 tables, 19 notes, 45 references, and 18 case citations.