Compounds of Formula I, including pharmaceutically acceptable salts of the compounds, are CETP inhibitors, and are useful for raising HDL-cholesterol, reducing LDL-cholesterol, and for treating or preventing atherosclerosis. In the compounds of Formula 1, A1 and A2 are each an aromatic ring, a 5-6-membered heterocyclic ring, an aromatic ring fused to a heterocyclic ring, a phenyl ring fused to a heterocyclic ring, or a cycloalkyl ring.