The company was accused of marketing its products to teenagers, causing a surge in use.

The Food and Drug Administration authorized Juul e-cigarettes for the U.S. market on Thursday, ending a lengthy standoff with regulators and lawmakers who accused the company of spurring an epidemic of e-cigarette use among youths.

The company was required to prove that the products were “appropriate for the protection of public health” under agency rules. Juul said in a statement that it met the bar, in part, by showing that its products had helped about two million adults quit smoking cigarettes.

The F.D.A. authorized both the e-cigarette system and menthol- and tobacco-flavored cartridges. Though concerns about the health effects of e-cigarettes are mounting, they are still widely viewed by experts as safer than cigarettes.

In a statement, a spokeswoman said the F.D.A. authorized the products based on “robust data” showing a high rate of adults switching from cigarettes to Juul products.

The agency said the action Thursday “does not mean these tobacco products are safe,” and that the agency will closely monitor the company’s compliance with rules to limit youth exposure to their marketing and will act if the company fails to comply.

“Today’s F.D.A. authorization of Juul products marks an important step toward making the cigarette obsolete,” K.C. Crosthwaite, the company’s chief executive, said in a statement.