The common motor neuron degenerative disease spinal muscular atrophy (SMA) results from reduced levels of the survival of motor neurons (SMN) protein. We found that the SMN protein is part of a large macromolecular complex (the SMN complex) that contains, in addition to SMN, at least six proteins called Gemins (2-7). The SMN complex, which is essential for all cells, functions in the biogenesis of the major components of the mRNA splicing machinery, small nuclear ribonucleoproteins (snRNPs), and appears to play a central role in cellular RNA metabolism. We have purified the SMN complex, reconstituted its activity in vitro, and defined its interactions with proteins and RNAs. Recent progress on the SMN complex and its relationship to SMA will be discussed