Abstract: In order to determine the relationship between rapid canopy closure and grain yield in wheat and to identify the traits that affect rapid canopy closure, a research was conducted using 5 wheat cultivars (Atrak, Tajan, Zagros, Golestan and Viniak). A field experiment with randomized complete blocks was carried out at the Gorgan University of Agricultural Science and Natural Resources, in 2003-2004. Rapid canopy closure had significant effect on grain yield, cultivars with faster canopy closure produced comparatively more grain yield per unit area. Leaf area index and seedling dry weight at the beginning of the exponential growth phase; relative leaf area development rate and relative growth rate during the exponential phase and the average of individual leaf area and leaf area ratio were detected as the effective traits in rapid canopy closure. It was concluded that the RCC is an appropriate way especially in the environment where growing season is limited and there is little scope for lengthening the growing season in order to increase dry matter production and yield.