Progress towards the laboratory demonstration of the steps in the prebiotic origin of the RNA world is reviewed. Montmorillonite clay catalyzes the formation of RNAs containing 6-14 monomer units from the activated mononucleotides of A, C, G, I and U. The RNAs formed have 3', 5'- and 2', 5'-links, pyrophosphate links and have both linear and cyclic chains. The purine oligonucleotides have more 3', 5'- links while the pyrimidine nucleotides have more 2', 5'-linkages. Template-directed synthesis on the heterogeneous oligo(C)s formed on montmorillonite yields the corresponding oligo(G)s. The dimer fraction formed in the reaction of a binary mixture of a purine and pyrimidine nucleotide shows sequence selectivity with about a 20 fold excess of the 5'-purine-pyrimidine dimer over that of the 5'-pyrimidine-purine dimer. RNAs as long as 50 mers are formed by the elongation of a decamer bound to montmorillonite by the daily addition of activated monomer to it over a 14-day time period.