Radiation curable and jettable ink compositions comprise ethylenically unsaturated 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 curable to form a cured ink having an elongation of at least 150%.