The extent of reaction in lightly cross linked poly(mono- and dimethacrylates) has been determined using solid- and liquid-state C-13 n.m.r. Three methods were used : (i) magic-angle spinning (MAS) with high-power decoupling of the solid; (ii) conventional liquid-state high-resolution n.m.r. of the samples swollen by CDCl3; (nl) m.a.s. of the swollen samples. The three methods give comparable results, indicating that motional factors which may affect the solid-state method are not significant.