FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person *   Chirumbole Frank W 2. Date of Event Requiring Statement (Month/Day/Year) 04/28/2011 3. Issuer Name and Ticker or Trading Symbol OLIN CORP [OLN] (Last) (First) (Middle) OLIN CORPORATION, 490 STUART ROAD, NE 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) President, Chlor Alkali Prod. 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) CLEVELAND, TN 37312 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock $1 par value 13,548 D   Common Stock $1 par value 712.0563 (1) I By ESOP Trustee

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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Employee Stock Option (right to buy)	02/14/2003	02/13/2012	Common Stock	12,000	$ 16.1	D	Â
Employee Stock Option (right to buy)	02/12/2005	02/11/2014	Common Stock	9,200	$ 18.52	D	Â
Employee Stock Option (right to buy)	02/10/2006	02/09/2015	Common Stock	9,200	$ 23.78	D	Â
Employee Stock Option (right to buy)	02/09/2007	02/08/2016	Common Stock	11,775	$ 20.68	D	Â
Employee Stock Option (right to buy)	02/13/2008	02/12/2017	Common Stock	10,250	$ 16.52	D	Â
Employee Stock Option (right to buy)	02/07/2009	02/06/2018	Common Stock	7,500	$ 20.29	D	Â
Employee Stock Option (right to buy)	02/05/2010(2)	02/05/2019	Common Stock	12,500	$ 14.28	D	Â
Employee Stock Option (right to buy)	02/05/2011(3)	02/04/2020	Common Stock	12,500	$ 15.68	D	Â
Employee Stock Option (right to buy)	  (4)	02/11/2021	Common Stock	14,000	$ 18.78	D	Â
Restricted Stock Units	  (5)	  (5)	Common Stock	3,333	$ (6)	D	Â
Restricted Stock Units	  (7)	  (7)	Common Stock	3,333	$ (6)	D	Â

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Chirumbole Frank W OLIN CORPORATION 490 STUART ROAD, NE CLEVELAND, TN 37312	Â	Â	  President, Chlor Alkali Prod.	Â

Signatures

/s/B. M. Pantalone		05/05/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The figure shown represents shares of Olin Common Stock held under the Olin Common Stock Fund of the Olin Corporation Contributing Employee Ownership Plan (CEOP), a tax-conditioned plan reflecting transactions exempt under Rule 16b-3, as reported by the Plan Administrator as of April 28, 2011.
(2)	Option vests in three annual installments beginning on 2/5/2010.
(3)	Option vests in three annual installments beginning on 2/5/2011.
(4)	Option vests in three annual installments beginning on 2/11/2012.
(5)	Right to acquire shares of common stock vesting on 2/5/2012.
(6)	Security converts on a one-for-one basis.
(7)	Right to acquire shares of common stock vesting on 2/5/2013.

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