Results of a study of sow inventory and pig supply responses are reported in this paper. Annual time series data (1953-54 to 1974-75) were used to estimate a two equation recursive model for Australia. Tests for structural changes in sow inventory response were conducted over time for Australian data and between regions for Victorian data. Single period lags of sow inventories, pig prices and feed prices were used to estimate short-run and long-run elasticities. The results yield information on pig supply additional to that presently available in the published literature. Evidence of structural change is reflected in elasticities of sow inventory response. While the hypothesis of structural change is statistically supported for regional aggregates of Victoria, the hypothesis of structural change over time was rejected using aggregate data for Australia.