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To evaluate the variations among and relations between agronomic traits, and seed yield and its components, 25 corn hybrids were planted on May 1st, 1998 in a randomized complete block design with four replications at Research Farm, College of Agriculture, Tehran University. Each plot consisted of four rows of seven meter length, with a row spacing of 75 cm and within row spacings of 20 cm. Twenty seven traits were evaluated using 10 competing random plants, obtained from within the middle two rows in each plot. Results of analysis of variance showed significant differences among hybrids, in terms of the traits under study, at 1% probability level. Hybrid varieties #6 (SC 715) and #10 (SC716) with mean yields of 13860 and 8416 kg/ha produced the most and the least, respectively. Correlation coefficeints indicated the highest correlation between seed yield and plant height. In a stepwise multiple regression analysis, plant height, 300-seed weight (gr), number of seeds/plant, number of days from planting to silk emergence and total number of leaves, explained 72.5% of total variations in seed yield. In factor analysis of traits, seven independent factors explained 79.5% of total variations in data. Phenological characteristics and corn leaf, as first and second factors, in total explained 40% of variation in data. Other factors were plant growth, yield components, number, characteristics of ear wood and ASI. In general, it can be inferred that under irrigation conditions, phenological traits, leaf characteristics, stem thickness, plant height, and also number of seeds/ear row can be considered as important criteria for selecting corn hybrids of high yield. The next other important traits to be considered are seed depth, ear diameter, number of seed rows, number of seeds/plant and 300-seed weight. Traits of diameter of ear wood, % ear wood, ASI and number of ears are considered to be of less importance.