Ca 2 RuO 4 , which has the single-layer tetragonal K 2 NiF 4 structure, shows nonmetallic behavior for TϽ300 K unlike its isostructural counterpart, Sr 2 RuO 4 , which is metallic for all TϽ1300 K and which undergoes a superconducting transition temperature below Tϭ1.35 K, possibly with p-wave spin pairing. Magnetization, electrical-resistivity, and heat-capacity data for single-crystal Ca 2 RuO 4 are presented. An antiferromagnetic transition is identified at T N ϭ110 K in all samples studied. The easy axis for magnetization is parallel to the a or b axis ͑in the Ru-O plane͒. Isothermal magnetization studies in fields to 30 T show a spin reorientation transition for Bϭ3.5 T at Tϭ105 K and a metamagnetic transition for TӶT N at about 9 T. The saturation magnetization even at 30 T, M sat Ϸ0.4 B /Ru, is less than expected for the Ru Sϭ1 moment (M sat Ϸ2.0 B /Ru͒. The electrical resistivity, (T), increases with decreasing temperature by eight orders of magnitude for 70ϽTϽ300 K and fits a variable-range hopping model including correlations. The magnetoresistivity below T N shows some dependence on spin orientation. In contrast to all the other Sr and Ca-based ruthenates, Ca 2 RuO 4 has a relatively small low-temperature electronic specific-heat coefficient ͑␥ϭ4 mJ/mole K 2 ͒, and unlike them, Ca 2 RuO 4 shows no anomaly in either (T) or d(T)/dT at T N . Some magnetization results are presented for lightly Sr-doped Ca 2 RuO 4 . The data are contrasted with those of metallic Sr 2 RuO 4 and discussed in terms of the weak spin disorder scattering in Ca 2 RuO 4 compared to the very strong coupling in the other Sr-and Ca-based ruthenates. ͓S0163-1829͑97͒50230-X͔