In order to identify nucleotide sequences required for efficient and accurate polyadenylation of mRNA precursors, we have constructed a series of mutations in the X. laevis beta 1-globin gene and analyzed transcripts produced upon microinjection into Xenopus oocytes. Small deletion and linker replacement mutations, which lie in the region from 8 to 39 bp downstream of the AATAAA sequence and which effectively remove previously identified second components of the polyadenylation signal, do not greatly reduce the efficiency of processing, but in some cases alter the precise site of cleavage. We conclude that sequences downstream of the polyadenylation site affect the position of 3' RNA processing, but have minimal effects on its efficiency.