Radiation-sensitive element comprising: (a) one or more types of monomers each comprising at least one ethylenically unsaturated group accessible to a free-radical polymerization, (b) at least one sensitizer, (c) at least one coinitiator capable of forming free radicals together with the sensitizer (b) and selected from the following classes of compounds: metallocenes; 1,3,5-triazine derivatives with one to three CX.sub.3 groups, wherein X represents chlorine or bromine; peroxides; hexaarylbiimidazoles; oxime ethers; oxime esters; N-aryl glycines and derivatives thereof; thiol compounds; N-aryl, S-aryl and O-aryl polycarboxylic acids with at least 2 carboxyl groups of which at least one is bonded to the N, S or O atom of the aryl unit; alkyltriarylborates; benzoin ethers; benzoin esters; trihalogenomethylarylsulfones; amines; N,N-dialkylaminobenzoic acid esters; aromatic sulfonyl halides; trihalogenomethylsulfones; imides; diazosulfonates; 9,10-dihydroanthracene derivatives; a-hydroxy and a-amino acetophenones; and (d) optionally one or more components selected from alkali-soluble binders, colorants, exposure indicators, plasticizers, chain transfer agents, leuco dyes, surfactants, inorganic fillers and thermopolymerization inhibitors characterized in that the at least one sensitizer is an oxazole derivative of the formula (I), wherein each R.sup.1, R.sup.2 and R.sup.3 is independently selected from a halogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, which may also be fused, an optionally substituted aralkyl group, a group --NR.sup.4R.sup.5 and a group --.sup.OR6, wherein R.sup.4 and R.sup.5 are independently selected from a hydrogen atom, an alkyl, aryl or ralkyl group, R.sup.6 is an alkyl, aryl or aralkyl group or a hydrogen atom and k, m and n are independently 0 or an integer from 1 to 5. ##STR00001##