Exhibit 21 ---------- SOUTH JERSEY INDUSTRIES, INC. SUBSIDIARIES OF REGISTRANT AS OF DECEMBER 31, 1997 Percentage of Voting Securities State of Owned by Parent Relationship Incorporation -------------------------------------------------- South Jersey Industries, Inc. Registrant Parent New Jersey South Jersey Gas Company (3) 99.06 (1) New Jersey Energy & Minerals, Inc. (3) 100 (1) New Jersey South Jersey Energy Company (3) 100 (1) New Jersey SJ EnerTrade, Inc. (3) 100 (1) New Jersey R&T Group, Inc. (3) 100 (1) New Jersey South Jersey Fuel, Inc. (3) 100 (2) New Jersey <FN> (1) Subsidiary of South Jersey Industries, Inc. (2) Subsidiary of Energy & Minerals, Inc. (3) Subsidiary included in financial statements </FN>