Parity establishes a compatible relationship whereby a change for one group (police or firefighters) automatically effects a related change for the other. In the 1950's, the assumption of a compatible relationship that permitted equal pay for firefighters and police began to be questioned by the police. The social turmoil of the 1960's, which reinforced demands for law and order, gave the police more power than firefighters to demand salary increases. Alliances supporting parity began to break down over such issues as personnel shortages, the nature of the workweek, training, and the degree of danger inherent in the work. Some claim that parity undermines the collective bargaining process, and many local governments view it as unnecessarily costly. The most frequently mentioned reason in favor of parity is morale. Firefighters claim that the curtailment of the parity principle will make firefighters feel their work is being devalued, which will in turn affect their work attitudes and performance effectiveness. The removal of parity clauses has been accomplished by the judiciary and State labor relations boards, using public employee enabling frameworks. Cities should develop guidelines to determine whether parity is justified for police and firefighters. These guidelines should cover such issues as the particular danger associated with urban police and fire service; the incidence of disabling injuries in the two services; recruitment, hiring and training; and retention and promotional probabilities. Standardization of these guidelines will help correct the varied treatment of the parity issue and introduce objective criteria for the decisions on parity between police and firefighters. References are provided.