Supply response and structural breaks during a 30-year period (1966-95) were evaluated. The Kalman filter procedure was applied in order to establish supply elasticities for six agricultural products. The results obtained concerning the agricultural supply response to changes in prices are interesting. High supply elasticities were obtained for beef and maize, while low elasticities were obtained for pork and potato, and very low supply elasticities were obtained for wheat and milk, perhaps indicating a high degree of State intervention (regulations) in the latter two individual agricultural markets in the past. The values of cross-price elasticities point at different complement and substitute relationships between various farm commodities.