Late 2006: Electronic cigarettes first marketed in U.S. via kiosks in shopping malls and online.
Early 2009: E-cigarette sellers sue the Food and Drug Administration after the agency told customs officials to refuse entry of shipments into U.S.
June 2009: The Food and Drug Administration said testing of products from two leading electronic cigarette makers turned up several toxic chemicals, including a key ingredient in antifreeze.
January 2010: Federal judge rules that the FDA can't stop those shipments, saying the agency had overstepped its authority.
December 2010: Federal appeals court rules e-cigarettes should be regulated as tobacco products by the FDA rather than as drug-delivery devices.
February 2011: U.S. Department of Transportation prohibits use of e-cigarettes on commercial airlines.
April 2011: FDA announces plans to regulate electronic cigarettes as tobacco products.
July 2011: FDA announces intent to have e-cigarette regulations proposed by October 2011.
April 2012: Lorillard Inc., the nation's third-biggest tobacco company, buys Blu Ecigs.
Summer 2012: No. 2 tobacco company Reynolds American Inc. begins limited distribution of first electronic cigarette under Vuse brand.
February 2013: The Centers for Disease Control and Prevention releases study showing increased awareness and use of electronic cigarettes in the U.S.
March 2013: Former U.S. surgeon general Dr. Richard Carmona joins board of directors for e-cigarette maker NJOY Inc.
July 2013: Reynolds American launches test market of revamped version of Vuse e-cigarette.
August 2013: Subsidiary of Altria Group Inc., owner of the nation's biggest tobacco company, Philip Morris USA, launches test market first e-cigarette under MarkTen brand name.
September 2013: CDC releases study showing growing use of e-cigarettes by middle and high school students.
End of 2013: Sales of e-cigarettes reach nearly $2 billion with more than 200 brands.
April 24, 2014: FDA issues proposed regulations for electronic cigarettes.