The Net gene encodes an Ets transcription factor belonging to the ternary complex factor subfamily. We studied Net expression during mouse development (E7.5–E18.5) by in situ hybridization. Net is expressed at E7.5–8.5 in developing vascular primordia, including the allantoic vessels, heart endocardium and dorsal aortae. Vascular endothelial cell expression persists throughout development. Additional sites of expression appear at E9.5–E10.5, especially in facial, branchial arch and distal limb-bud mesenchyme. Later, expression is most conspicuous in developing cartilage and becomes progressively restricted to perichondrium. Net expression during mouse development correlates with vasculogenesis, angiogenesis and cartilage ontogeny.