Technical Abstract: Mutations can make profound impact on the evolution and improvement of a self-pollinated crop such as lettuce. Since it is nontransgenic, mutation breeding is more acceptable to consumers. Combined with genomic advances in new technologies like TILLING, mutagenesis is becoming an even more powerful tool for lettuce breeders. It is primarily a means of creating genetic variability, which can then be utilized in physiological or genetic studies and cultivar development. It is most effective to alter qualitative traits under the control of major genes such as disease resistance, development, and quality, rather than quantitative traits like yield and adaptation. Due to the random nature of mutagenesis, a large population of mutated individuals needs to be established to be practically useful. That requires input of great amount of time, labor, facility, and effort. It would be very cost-effective if such a mutant population is established with seeds maintained in a public genebank, and the lettuce breeding and research community can request seeds to screen for various beneficial traits. Mutagens have been employed for some 90 years to modify plants for human needs, and their use will only be explored by more and more lettuce researchers in the future.