The D. melanogaster dunce gene is involved in both the learning and memory processes of the fly. The gene encodes for a cAMP-specific phosphodiesterase, a function playing a central role in the regulation of the intracellular cAMP level. Molecular cloning of dunce has so far not been completely achieved, although it is known that the gene encodes a large set of RNAs and has a complex organization, extending for more than 140 kilobases and containing several genes within its introns. Here we report the isolation and the characterization of 21/7, a cDNA clone representative of a novel dunce splicing pattern. The nucleotide sequence of this clone led to the identification of a dunce exon included in at least one transcript so far uncharacterized.