SID Companhia Siderurgica Nacional

  Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.  

COMPANHIA SIDERÚRGICA NACIONAL

Publicly-Held Company

Corporate Taxpayer's ID (CNPJ/MF) No. 33.042.730/0001-04

State Registry (NIRE) No. 35-3.0039609.0

MATERIAL FACT

Companhia Siderúrgica Nacional (BOVESPA: CSNA3; NYSE: SID) (“CSN” or “Company”),  pursuant to Article 157, Paragraph 4, of Law 6404/76, as amended and to the Instruction of the Securities and Exchange Commission (“CVM”) No. 358/02, as amended, informs its shareholders and the market in general that, in exceptional circumstances, it will not make available the Quarterly Statement for the first quarter of 2017 ("1 ^st QS 2017") within the period established by CVM Instruction No. 480/09, due to the review of the accounting treatment agreed for the operation carried out by the Company on November 30, 2015, which resulted in the combination of the mining and related logistics businesses, without modification of its business structure. This review affects the Financial Statements for the fiscal year ended on December 31, 2015 and consequently affects the opening balances of the Financial Statements for the year ended on December 31, 2016 ("FS 2016") and for the 1 ^st QS 2017.

However, considering the duty to inform and act with diligence and transparency, the Company decided to disclose to the market the main operating indicators of the first quarter of 2017, not yet reviewed by our independent auditors, which are not affected by these potential adjustments that may arise as a result of the reviews that are in progress, as follows:

¹ Iron ore sales volumes include 100% of the stake in NAMISA until November 2015 and 100% of the stake in CSN Mineração (former “Congonhas Minérios”) as of December 2015. As of December 2015, iron ore volumes include sales to UPV.

² Adjusted EBITDA is calculated based on net income/loss, plus depreciation and amortization, income tax, net financial result, results from investees, other operating income (expenses) and includes the proportional share of EBITDA of the jointly-owned investees MRS Logística and CBSI. Adjusted EBITDA includes the 60% stake in Namisa, 33.27% in MRS and 50% in CBSI until November 2015 and the 100% stake in CSN Mineração, 37.27% in MRS and 50% in CBSI as of December 2015.

³Adjusted net debt and adjusted cash include the 33.27% stake in MRS, 60% in Namisa and 50% in CBSI until November 2015. As of December 2015 these lines include the 100% stake in CSN Mineração, 37.27% in MRS and 50% in CBSI, and exclude Forfaiting and Debtor Risk operations.

⁴ The managerial financial result includes the 60% stake in Namisa, 33.27% in MRS and 50% in CBSI until November 2015 and the 100% stake in CSN Mineração, 37.27% in MRS and 50% in CBSI as of December 2015.

⁵ From 2017, CSN will simultaneously disclose the iron ore price CFR + FOB and, for comparative purposes, we adjusted the previous quarters.

The Company is committed to disclosing the Financial Statements for 2016, as well as the 1 ^st ITR 2017, as soon as possible. The sooner the date for the completion of the work is established, the Company will disclosed it to the market.

São Paulo, May 15, 2017.

David Moise Salama

Investor Relations Executive Officer