Radiation curable and jettable ink compositions comprise ethylenically un saturated oligomer and an ethylenically unsaturated monofunctional monomer. The compositions may optionally include additional ethylenically unsaturated polyfunctional component and/or chain transfer agent. The compositions have a viscosity at 25°C of not greater than about 70 cPs and are radiation cura ble to form a cured ink having an elongation of at least 150%.