Catalytic hydroalkoxylation/cyclization reactions of alkynyl and allenyl alcohols are efficiently mediated by homoleptic lanthanide amides Ln[N(SiMe3)(2)](3) (Ln = La, Nd, Sm, Y, and Lu). Conversions are found to be highly selective with products distinctly different from those produced by conventional transition metal catalysts. Turnover frequencies as high as 18.0 h(-1) at 60 degrees C are observed. Kinetic studies indicate that these transformations are zero-order in [substrate] and first-order in [catalyst]. Catalytic cycles are proposed in which insertion of C-C unsaturation into a Ln-O bond is turnover-limiting.