General Motors Co
GM sold 221,192 vehicles in the month, down from 223,822 in May 2010 when results included four brands the company no longer sells.
U.S. auto sales figures offer one of the first snapshots of consumer demand in May. The rest of the automakers are scheduled to report their May sales later on Wednesday.
Economists polled by Reuters projected the industrywide annualized sales rate would be around 12.6 million in May, 8.6 percent higher than in May 2010.
But if these forecasts prove true, this will be the first time the annualized sales rate has dropped below 13 million since February. The May sales numbers come as analysts are raising concerns about a slowdown in the broader economy.
(Reporting by Ben Klayman in Detroit, editing by Matthew Lewis)