Plaintiff, employees of United States Steel Corporation, filed suit on August 25, 1976, against appellants, Koppers Co., Inc., and Allied Chemical Corporation, and co-defendant Salem Corporation for personal injuries and/or wrongful deaths caused by occupational exposure to substances emitted by coke ovens at the premises of United States Steel Corporation. Appellant, Koppers, filed a third party complaint against appellee, United States Steel (USS) seeking contribution or indemnity. USS filed Preliminary Objections in the nature of a demurrer contending its joinder was precluded by the amended Section 303 of the Pennsylvania Workmens Compensation Act, Act of Dec. 5, 1974, P.L. 782, No. 263, ? 6, 77 P.S. ? 481(b) (Supp.1978-79). The Preliminary Objections dismissing appellee from the suit were sustained and that decision was affirmed per curiam, with one dissent, by the Superior Court. 253 Pa. Super. 590, 384 A.2d 980 (1978). We granted appellants Petitions for Allowance of Appeal on June 2, 1978 and this appeal followed.