The economics of a number of pasture renovation options were evaluated using a Partial Budget Model. The analysis took into account changes in income (milk, hay and livestock sales), variable costs (feed, shed, herd and casual labour) and overhead costs (depreciation of livestock) resulting from the management changes associated with the pasture renovation scenarios Oversowing of pastures with either perennial ryegrass or short-lived ryegrass, in a system in which cow numbers were altered in response to changes in pasture supply, resulted in increased pasture consumption, higher stocking rates, increased milk production, increased income and increased gain after costs. These benefits of oversowing occurred in both medium and high concentrate feeding and split calving systems. Analysis of the resowing of pastures showed that the reduction in pasture consumption in the year of resowing necessitated increased concentrate inputs. This increase in feed costs is approximately double that of the actual pasture resowing costs. The time to breakeven is dependent upon the productivity level of the initial pasture and the species sown.