Tyrosine 3-hydroxylase was analyzed for activity in gel and in HPLC as the catechol-related enzyme in Mox^GM95, a phenol oxidase activity-deficient variant, in Drosophila melanogaster. A single band of tyrosine 3-hydroxylase in the gel was detected in native PAGE, and a peak of L-dopa from L-tyrosine was presented. Higher frequencies of non-sexual locomotor activity and sexual behavior comprising male wing flicks and female mating propensity were seen in Mox^GM95 than in Mox, whereas more latent behavior comprising non-sexual climbing activity was seen in Mox^GM95. These results show that Mox^GM95 is not always defective in phenol oxidase activity, and is not defective in behavioral activity.