The cyclization of 1-en-6-ynes catalyzed by PtCl2 in the presence of water or alcohols affords five or six-membered ring carbocycles containing hydroxy or alkoxy functional groups in high yields. The alkoxycyclizations can also be performed with AuCl3 as catalyst. The reaction is stereospecific, atom-economical, and takes place in environmentally friendly solvents.