OBJECTIVES: Prior authorization (PA) is a managerial technique frequently implemented to curtail use of expensive drugs and to improve drug-prescribing quality.  PA requirements may incentivize physicians to document adverse effects (AEs) to drugs, sometimes falsely, to meet eligibility-requirements for approval. The objective of this study was to evaluate the effect of a PA requirement on documentation rates of AEs of drugs necessary for approval of more expensive drugs. METHODS: We conducted a retrospective analysis of physician electronic-reporting behavior of AEs to angiotensin converting enzyme inhibitors (ACE-Is) before and after revocation of a PA requirement for angiotensin receptor blockers (ARBs) during the years 2004-2013 in an Israeli HMO. Data were stratified by newly treated and patients who had been treated for at least one year. The annual rate of AEs to ACE-Is in treated patients (number of reported cases of AEs per 1000 ACE-I treated patients) was calculated for the five years before and after revocation of the PA constraint.   RESULTS: CONCLUSIONS: The PA requirement under investigation was observed to be significantly associated with physician propensity for reporting drug side-effects, possibly erroneously. The decline in incidence of reported of side-effects in both subpopulations upon revocation of the PA requirement confirm our suspicion that physicians were incentivized to document side effects to ACE-Is to meet eligibility-requirements for approval of ARBs. The risk of gaming behavior in documentation of drug side effects may increase when side effects cannot be substantiated with laboratory tests or diagnostic imaging.