HUMAN motor neuron (MN) isolation provides a critical tool to study neurophysiological properties and the effects of molecules of clinical relevance on isolated neurons. We developed an immunomagnetic separation technique based on specific MN antigen recognition for nerve growth factor receptor (p75-NGFR). We cultured an average of 250 000 cells from the anterior horns of a single cord (four specimens at postconception Weeks 6.0, 7.2, 8.0, and 8.3). At day 7in vitro(DIV), choline acetyltransferase (ChAT) and/or p75-NGFR-expressing cells (MNs) represented 72 ± 2% of the total growing cells. MNs survived for at least 4 weeks in biochemically defined medium. The immunomagnetic separation method has been demonstrated to be effective, reproducible, and quantitative for separation of MNs.