Bulk single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3–5 at.% in the near-surface (∼2000 Å) region. The implantation was performed at ∼350 °C to promote dynamic annealing of ion-induced damage. Following annealing at 700 °C, temperature-dependent magnetization measurements showed ordering temperatures of ∼300 K for Co- and ∼250 K for Mn-implanted ZnO. Clear hysteresis loops were obtained at these temperatures. The coercive fields were ⩽100 Oe for all measurement temperatures. X-ray diffraction showed no detectable second phases in the Mn-implanted material. One plausible origin for the ferromagnetism in this case is a carrier-induced mechanism. By sharp contrast, the Co-implanted material showed evidence for the presence of Co precipitates with hexagonal symmetry, which is the cause of the room temperature ferromagnetism. Our results are consistent with the stabilization of ferromagnetic states by electron doping in transition metal-doped ZnO predicted by Sato and Katayama–Yoshida Jpn. J. Appl. Phys. 40 (2001) L334. This work shows the excellent promise of Mn-doped ZnO for potential room temperature spintronic applications.