Development of plant-to-plant variability in plant height, flowering characteristics and grain yield was studied in two maize (Zea mays L.) hybrids grown over 2 yr at 62 000, 93 000 and 124 000 plants/ha. The purpose of the research was to provide fundamental data on patterns of interplant variability in maize, as a foundation for more applied studies on effects of cultural practices on within-crop variability and yield. Plant height was normally distributed early in the season but tended to become negatively skewed as the plants grew. The same tendency for negative skewness existed in calculations of rate of elongation. The standard deviations of height and of rate of elongation increased as plants enlarged. Frequency distributions of days to anthesis or silking were positively skewed as was the distribution of number of days from anthesis to silking at high density. The standard deviations of days to silking, and days from anthesis to silking increased with increasing density. Grain yield per plant was normally distributed or slightly skewed negatively, with barren plants not considered. With the latter included, frequency distributions were bimodal at higher densities. The standard deviation of plant height increased as the crop developed although the coefficient of variability of height declined. Plants which were initially short did not "catch up" in height until after flowering had begun. Taller plants tended to anthese and silk earlier and produce more grain; in general, these associations were stronger with measurements of height taken prior to flowering than after. Date of silking was more closely related to yield than date of anthesis. On average, plants destined to be barren were shorter than the population mean on all dates of measurement and retarded in development. However, many plants became barren which were taller than average and earlier than average in date of flowering.Key words: Competition, maize, barrenness, grains, height, silking