There has been a trend toward narrower row width and an increase in plant population for corn (Zea mays L.) production in the northern Corn Belt. The impact of corn hybrid and plant population on grain yield may be influenced by row width. This study was designed to investigate the relationships between row width, plant population, and hybrid at three Minnesota locations from 1992 through 1994. At Lamberton and Waseca, row widths were 10, 20, and 30 in.; target populations were 25 000, 30 000, 35 000, and 40 000 plants/acre; and hybrids were Ciba 'G4372,' DeKalb 'DK512,' and Pioneer Brand 'P3563'. At Morris, the same row widths were evaluated but the target populations were 22 000, 27 000, and 32 000 plants/acre and the hybrids were Northrup King 'N3624,' DeKalb 'DK421,' and Pioneer Brand 'P3751'. At Lamberton and Waseca, the yield advantage for both 10- and 20-in. rows compared with 30-in. rows was 7.2% when averaged over all hybrids and all plant populations, whereas at Morris the yield advantage was 8.5%. Choice of hybrid influenced grain yield, and all hybrids responded similarly to change in row width and change in plant population at the three locations. Grain yields increased at Lamberton and Waseca with higher plant populations in 1992 and 1994, but not in 1993 when yields were limited by climatic conditions. Regression analysis of yield vs. harvest plant population showed yields were highest at populations at or above 35 000 plants/acre in 1992 at Lamberton and 1994 at Waseca and Lamberton, but were unaffected by plant populations in 1992 at Waseca and in 1993 at both locations. At Morris, regression analysis of yield vs. harvest plant population in 1993 and 1994 showed yields were highest at plant populations of 32 000 plants/acre, the highest plant population studied at that location. Choice of hybrid and the growing season climatic conditions had a greater effect on grain moisture content at harvest, test weight, and ear length than row width or plant population. These data show a yield advantage for narrowing row widths from 30 to 20 or 10 in., and that in some years maximum yields were obtained at harvest plant populations substantially higher than the current Minnesota population of 26 400 plants/acre.