Evidence is accumulating that axonal members of the lg superfamily (IgSF) interact in a complex manner with other axonal Ig-like proteins and with proteins of the extracellular matrix. Studies investigating the structure/function relationships of these proteins have highlighted the importance of Ig-like domains near the amino terminus (N-proximal) as both necessary and sufficient for homophilic and heterophilic binding. Although efforts have been made in the past year to correlate the structure and neurite-outgrowth-promoting ability of axonal IgSF members, this work is still at an early stage.