We have specimens of a slug collected in late 1992 from the west side of Ann Arbor, Washtenaw Co., Michigan. The slugs appeared to belong to the Arion hortensis species complex. Our examination of external anatomy as described by Davies (1977, 1979) and Cameron et al. (1983), and our examination of internal anatomy (the distinct flap at the base of the epiphallus that has characteristic species-specific shapes) as described by Davies (1977, 1979) revelaed that the slugs are A. hortensis s.s. This note is the first report confirming that A. hortensis s.s. is present in Michigan.