1. Intimal migration and proliferation causing artery stenoses in the course of atherogenesis can be inhibited by various drugs. 2. Secondary stenoses after ballooning of arteries are caused mainly by proliferation of smooth muscle cells. 3. Ballooning of arteries or repeated transmural electrical stimulations of artery walls with weak electrical current is followed by an increased mitotic activity of smooth muscle cells in the ballooned resp. stimulated area which reaches a maximal value about one week following the onset of the experiment. The mitotic activity returns then slowly to initial levels. 4. Adaptations to proliferation-inducing stimuli are possible. The experiments demonstrate that the proliferative phases in atherogenesis can be explained as a sequence of adaptations and deadaptations (= change of disposition) to the proliferation-inducing stimuli. 5. To select qualified drugs for an inhibition of the development of intimal proliferates in the course of atherogenesis makes it necessary to combine in vivo tests in animal experiments with tests on cell cultures of human cells from artery walls.