Acetohydroxyacid synthase (AHAS) is the target enzyme for a number of herbicides. A S653N mutation in the AHAS gene results in an increased tolerance to imidazolinone herbicides. We have investigated the use of the mutated gene as selection gene for potato transformation. This resulted in a transformation system with a very high transformation frequency and low rate of escapes. The mutated AHAS gene was introduced into transformed potato together with a beta-glucuronidase (GUS) gene. Selection on 0.5 microM Imazamox yielded GUS expression in 93-100% of regenerated shoots. Furthermore the mutated AHAS gene was used as selection gene for production of high-amylopectin potato lines. The high transformation frequency was verified and potato lines with the desirable starch quality were obtained.