Rate studies of complexation reactions of macrocycles reacting with metal cations in nonaqueous solutions are reviewed. Particular attention is given to differing mechanistic pictures arising from ultrasonic absorption and nuclear magnetic resonance studies of crown ethers in a variety of nonaqueous solvents. Future directions of complexation kinetic studies are also considered. Macrocycles, Crown ethers, Nonaqueous solutions, Ultrasonic absorption, Nuclear magnetic resonance, Cation complexation kinetics.