Polyunsaturated diazonium compounds suitable for use in negative working radiation sensitive compositions are provided. They may be produced by reacting an aromatic diazonium compound of the formula(A.sup.- N.sub.2.sup.+)p--Ar--(R)q--(XH)rwith a polyethlenically unsaturated monoisocyanate compound of the general formula ##STR1## where p and q are integers ranging from 1 to 5, r is an integer ranging from 1 to 10; Ar represents a substituted or unsubstituted divaient or polyvalent radical derived from an aromatic or heteroaromatic compound; X represents O, S or a secondary or tertiary amino group; R represents a single bond or a substituted or unsubstituted divalent or other polyvalent radical and may be the same or different when q is greater than 1; A.sup.- represents an anion; Z represents the residue of a polyisocyanate OCN--Z--(NCO)n where n is 1 or 2; and Y is the residue of a monohydroxy compound of the formula YOH where Y contains at least two ethylenically unsaturated double bonds.