Bisaldolization of aryl alkyl ketones as well as cyclic ketones with paraformaldehyde in the presence of a catalytic amount of l-proline and low concentration of aqueous sodium hydroxide has been developed in excellent yields. Further, these bisaldols are elaborated to the corresponding spirocyclic dioxanes and novel spirocyclic trioxocanes in the presence of p-toluene sulfonic acid. The structures and preferred conformations of these eight-membered spirocyclic 1,3,5-trioxocanes are discussed.