This research was conducted with the objective of determining the effect of the critical period of weed competition on rice yield transplant Capirona variety, the period of competition "global and critical weed with rice" and the analysis economic treatments by cost-benefit balance. The study was conducted between November 1, 2000 until March 15, 2001 on the property of Mrs. Carmen Garcia Ramirez; located in the District of Morales, province of San Martin, under the randomized complete block design with 16 treatments and 3 repetitions. The best yields of paddy were obtained in treatments without weeds throughout the season (T1) (8 352.59 kg / ha) and weeding until 30 to 60 days T1 and T4 (7 826.66 and 7 308.03 kg / ha ), with weeding from 10 and 50 days T14 and T13 (7 y7037.03 394.74 kg / ha) after transplantation. The critical global competition transplant rice with weeds, period ranges...