This paper explores the role of management ability in explaining efficiency on New York dairy farms. Using an unbalanced panel of farm data from 1993 through 2004, we estimate input and output-oriented technical efficiencies, cost efficiencies and revenue efficiencies using stochastic frontier functions. We include various input variables as efficiency effects and find lagged net farm income is a preferred measure of management ability over farmers' own estimates of the value of their labor and management. We also find increasing efficiency with operator education, farm size, and extended participation in a farm management program and decreasing efficiency with operator age.