Abstract: The invention relates to radiation curable compositions. The invention provides radiation curable optical fiber primary coating compositions comprising an oligomer, a reactive diluent monomer blend comprising at least two reactive diluents monomers, and at least one photoinitiator, wherein each of said monomers in said blend has the formula (I) wherein x is an integer of from 1 to 6; n is an integer of from 1 to 5; and each Y, which may be the same or different, is independently selected from the group consisting of hydrogen, a C1 to C12 alkyl group and an alkarylalkoxylated acrylate radical; and at least one photoinitiator; said reactive diluent monomer blend being substantially free of non-aryl reactive diluent monomers; wherein when an aryl reactive diluent monomer is present that has a molecular weight less than about 300, it is present at no more than about 10 wt. % of the total formulation.