1. A goldfish AMPA-type glutamate receptor cDNA (GFGR49) was cloned from a goldfish retinal cDNA library. 2. The GFGR49 clone is an immature product of pre-mRNA, possessing the C-flip exon and flanking introns. 3. RNase protection assays revealed multiple mRNAs that contain the C-flip exon. In addition, these assays indicated differential processing of these RNAs between retina and brain. 4. Finally, RNase protection assays employing probes spanning the 3'-coding region of GFGR49 revealed at least two different mRNA phenotypes. 5. Comparison with the sequence of genomic DNA, which was obtained by polymerase chain reaction amplification, suggests that such multiple mRNA phenotypes are attributed to the use of alternative intron-exon splicing junctions and to RNA editing.