Analogues of yeast alanyl tRNA with I_(34) replaced by A_(34) or G_(34) were synthesized. Synthetic analoguesof yeast alanyl tRNT occupy the same position as the natural yeast alanyl tRNA on polyacrylamide gelelectrophoresis, and their purity is about 95% after electrophoresis on a 10% or 20% polyacrylamide gel.The two terminal and nearest neighbour nucleotides of the analogues are all correct. The accepting acti-vity of the synthetic analogues is similar to that of the reconstituted natural yeast alanyl tRNA. The in-corporation activity of alanine into proteins of the synthetic analogues is about 30% of that of the naturalof reconstituted natural yeast alanyl tRNA when I_(34) is replaced by A, and is 90% when I_(34) is replaced byG.The reason of the variation in biological function of the analogues of yeast alanyl tRNA after I_(34) re-placed by A or G was discussed. Analogues of yeast alanyl tRNA with I_ (34) replaced by A_ (34) or G_ (34) were synthesized. Synthetic analogues of yeast alanyl tRNT occupy the same position as the natural yeast alanyl tRNA on polyacrylamide gelelectrophoresis, and their purity is about 95% after electrophoresis on a 10% or 20% polyacrylamide gel. The two terminal and nearest neighbor nucleotides of the analogues are all correct. The accepting acti-vity of the synthetic analogues is similar to that of the reconstituted natural yeast alanyl tRNA. The in- corporation activity of alanine into proteins of the synthetic analogues is about 30% of that of the natural of reconstituted natural yeast alanyl tRNA when I_ (34) is replaced by A, and is 90% when I_ (34) is replaced by G. The reason of the variation in biological function of the analogues of yeast alanyl tRNA after I_ (34) re-placed by A or G was discussed.