The present invention relates to a radiation-curable ink-jet ink comprising at least two monofunctional (meth)acrylate monomers; a monofunctional monomer selected from an N-vinyl amide, an N-acryloyl amine, or a mixture thereof; a polymerisable (meth)acrylate oligomer; a radical photoinitiator; and a colouring agent; wherein the ink has a viscosity of less than 100 mPas at 25° C. The ink is substantially free of multifunctional monomers; and the at least two monofunctional (meth)acrylate monomers include a combination of a cyclic monofunctional (meth)acrylate monomer and an acyclic-hydrocarbon monofunctional (meth)acrylate monomer. The ink displays an excellent balance of cure speed and viscosity for the ink together with hardness and flexibility for the cured film.