This paper uses a DNA-fingerprinting based varietal identification approach to estimate adoption rates of improved cassava varieties in Nigeria. By applying a procedure that combines marginal treatment effects with a market-level model, the paper measures the counterfactual household income distributions for adopters. The paper then estimates poverty impacts of adoption of improved cassava varieties based on the differences between observed and counterfactual income distributions. Our results suggest that adoption of improved cassava varieties has led to a 4.7 percentage points poverty reduction at a poverty line of $1.25 per person per day (or 2.7% points poverty reduction if poverty line of $1.9 per person per day poverty line was considered). The analysis further suggests that farmers who are more likely to adopt improved varieties are also likely to face higher structural costs. Relaxing structural barriers that make improved technologies inaccessible and less profitable for poor households would therefore be important to maximize the poverty reduction roles of improved technologies such as cassava varieties. Further, we find that the poverty effects of adoption are very sensitive to the measurement of adoption status. Therefore, proper measurement of adoption status is crucial for estimating the poverty reduction effects of adoption accurately. Acknowledgement : This research was co-supported by the Bill and Melinda Gates Foundation (BMGF) under the grant the Cassava Monitoring Survey in Nigeria , the Roots, Tubers and Bananas (RTB) Research Program of the CGIAR and the ISPC-SPIA under the grant Strengthening Impact Assessment in the CGIAR System (SIAC). The contributions of Godwin Ashumuga, Peter Kulakow and Alfred Dixon to the conceptualization and design of this project is gratefully acknowledged. Field supervisors, enumerators, extension agents, NRCRI staffs and IITA staff from socioeconomics, bioscience, and cassava breeding units are recognized and thanked for their contributions.