The length of the growing cycle is one of the most important traits determining hybrid adaptability to the environment. The objective of this work was to study the development, dry matter accumulation, grain yield, harvest index, and sink-source relationship of 11 maize (Zea mays L.) hybrids with contrasting maturity. The durations of the cycle from emergence to flowering varied from 537 to 781 growing degree days and from emergence to physiological maturity from 1221 to 1656°Cd. Cumulative biomass from emergence to flowering increased linearly with hybrid cycle length. Long-season hybrids showed the highest cumulative interception but the lowest radiation use efficiency (RUE) during reproductive growth. Total aboveground biomass increased from 1624 to 2422 g m 22 with hybrid maturity class, and grain yields were lowest for short-season hybrids (832 g m 22 ) and similar between mid and long-season hybrids (avg. 5 1256 g m 22 ). Increases in maturity class were associated with increases in grain number (from 2432 to 5078 grains m 22 ) and reductions in individual grain growth rate (from 9.1 to 4.9 mg grain 21 d 21 ). The sink-source relationship and the apparent reserve remobilization increased with hybrid maturity class. These results indicate that grain yield of shortseason hybrids would be more limited by the capacity of the reproductive sinks during grain filling than their long-season counterparts. Hybrids Ax 840 and Experimental have a short developmental time from emergence to flowering but a long developmental time from flowering to physiological maturity. This resulted in the largest values of radiation interception during reproductive growth and in the greatest grain yields and harvest indexes.