Sulfur response in corn (Zea mays L.) has been increasing on medium and fine textured soils in the northern Corn Belt.  However, little to no recommendations have been developed for application rates when responses occur and when fertilizer should be applied.  The objective of this study was to determine corn response to rates of S fertilizer applied at planting or as an early side-dress application.  Five rates of sulfur were applied as ammonium sulfate (21-0-0-24 N-P-K-S) at rates of 0, 11.2, 22.4, 33.6, and 44.8 kg S ha^-1.  Fertilizer was applied to the soil surface immediately after corn planting and at the V4-V5 growth stage.  Corn yield was increased by the application of sulfur at three of seven locations.  Two responsive locations were previously cropped with corn, and one soybean (Glycine max (L.) merr.).  The rate that returned the greatest yield was 11.2 kg S ha^-1 at two locations and 22.4 at the other.  When corn grain yield responded to S, there was no difference between application timing.  However, grain moisture was sometimes higher when sulfur application was delayed until V4-V5.  The results indicate that corn can respond to sulfur on medium and fine textured soils and the rate needed to maximize yield is less than recommended for corn grown on coarse textured soils.