This study estimates the adoption gap of NERICA that exists in the population when access to seeds is a constraint. Treatment evaluation technique is applied to con-sistently estimate the potential NERICA adoption rate and its determinants using panel data from a stratified random sample of 515 rice farmers in The Gambia. The results show that the NERICA adoption rate could have been 76% instead of the observed 66% sample estimate in 2010 provided that every rice farmer had been aware of NERICA’s existence before the 2010 rice growing season. However, further investigation finds that if all the rice farmers had been aware of and had access to NERICA seeds, adoption would have been 92%. This reveals that if awareness had not been a constraint, 16% of farmers would have failed to adopt NERICA due to lack of access to seeds. Farmer contact with extension services and access to in-kind credit are significant determinants of access to and adoption of NERICA varieties.