EXHIBIT 21 SUBSIDIARIES OF UNITED STATIONERS INC. UNITED STATIONERS INC. UNITED STATIONERS SUPPLY CO. AZERTY INCORPORATED LAGASSE BROS., INC. AZERTY de MEXICO, S.A. de C.V. UNITED WORLDWIDE LIMITED UNITED STATIONERS HONG KONG LIMITED SAH, INC. USS RECEIVABLES COMPANY, LTD. UNITED BUSINESS COMPUTERS, INC.