As the world tries to make sense of the U.K.'s historic vote, three sectors could be especially hard hit.
First, there's the automotive industry. Last year, nearly 1.6 million cars were made in the U.K., with 77 percent being exported. Nearly 58 percent of exported autos went to European Union countries.
On Friday, Rolls-Royce's U.S.-listed shares fell 7.3 percent.
Then there's the airlines business, which might have to deal with new European routes, as well as higher taxes.
U.K.-listed shares of British airline EasyJet fell more than 20 percent in the premarket Monday after raising concerns about its third-quarter results, partially citing the Brexit vote.
Lastly, there's the pharmaceutical industry.
Pharma giants like GlaxoSmithKline and AstraZeneca do a large part of their business overseas and could face significant headwinds because of Brexit.
U.S.-listed shares of GlaxoSmithKline were down 2 percent in the premarket; AstraZeneca was up slightly.