Spiropyrazolines have been synthesized by 1,3-dipolar cycloaddition of an 2-arylidene-1-tetralone, 3-arylidene-chromanones, -1-thiochromanones, and -flavanones with diazomethane. The relative configuration and stereochemistry of the products have been determined by means of one-dimensional difference N.O.E. measurements. It is shown that ring-closure reaction is regioselective, yielding stereohomogeneous spiropyrazolines in one step.