The fretting wear arises when contacting surfaces undergo oscillatory tangential displacement of small amplitude. Depending on the degree of stick and slip there are three kinds of the contact motions, such as gross-slip, partial-slip and stick-slip. The fretting damage occurs most severely when the transition from gross-slip to partial-slip happens. In this paper, the transitions of friction and wear under fretting were investigated by ball-on-disk wear tests in various environments, which were dry friction of air and nitrogen, and wet friction of mineral oil and engine oil. The transition from partial-slip to stick-slip firstly occurred in nitrogen environment, and then in air. Later, the transition occurred at higher load in mineral oil, and then lastly in engine oil.