Crown rust, caused by the fungal pathogen, Puccinia coronata, severely reduces kernel quality and grain yield in oat. Partial resistance is considered to be a durable form of rust resistance. The objectives of this study were to evaluate the effectiveness of index selection as a method for improving partial resistance to crown rust, grain yield and seed weight in oat population, and to estimate heritabilities for area under disease progress curve (AUDPC) and genetic correlations between AUDPC and agronomic traits in both crown rust-inoculated and fungicide-treated plots. A single cycle of selection for partial resistance to crown rust was performed. The initial (CO) and selected (Cl) generations of two oat populations were evaluated in a field experiment in 2001 and 2002 at two Iowa locations. The selection, via a selection index, increased the levels of crown rust resistance and grain yield and seed weight in crown rust-inoculated plots, and seed weight in fungicide-treated plots. However, there was no significant change for the grain yield in the disease-free environment. In both CO and Cl population, AUDPC were highly heritable, and were favorably correlated with grain yield, seed weight and test weight measured in crown rust-treated plots. Realized heritabilities for all traits but grain yield under the disease-free environment were relatively high. Our results suggested that the index selection as a method for selecting oat lines with high levels of crown rust resistance, grain yield and seed weight is possible.