In this talk an account is given of the author's use of 4-alkynoic acid derivatives in the synthesis of members of the chlorin, bacteriochlorin and corrin classes of macrocyclic tetrapyrroles. In the case of chlorins, we employed a novel "2+2" condensation to prepare both C,D-symmetric and non-symmetric chlorins, made possible by the ready availability of highly substituted semicorrins derived from 4-alkynoic acids. Alkyne acids also played a prominent role in a new 16p-electrocyclization route to bacteriochlorins, and in iterative syntheses of semicorrins and secocorrins related to vitamin B₁₂. Finally, we describe enantioselective syntheses of ring-C and ring-D alkyne acids for a proposed synthesis of cobyric acid.