The present study analyzes the reliability of data on compliance with Constitutional Amendment 29 (CA29) reported to the Public Healthcare Budget Information System (known as SIOPS) by municipalities in the State of Pernambuco, Brazil. A quantitative, analytical cross-sectional study was conducted using the years 2000 to 2005 as the reference. Invoices audited by the State Accounts Court were used as the parameter for determining reliability of the percentage of compliance with CA29 as reported to SIOPS, using the intraclass correlation coefficient (ICC) to measure data agreement. The results show a mismatch between the databases, suggesting slight to moderate agreement between the SIOPS data and those from the State Accounts Court. The low degree of agreement may result from lack of consensus among municipalities regarding definition of health-related revenues and expenses or the existence of different criteria used by SIOPS and the State Accounts Court for calculating the CA29.