Excluding volatile food and energy goods, the "core" consumer price index (CPI) rose 3.8 percent over the last year, without seasonal adjustment, "the largest 12-month increase since the period ending June 1992," the Labor Department said.
CPI rose 0.6 percent last month, seasonally adjusted, slower than in April but higher than the consensus forecast. Core CPI increased 0.7 percent.
One third of the rise was due to used cars, which rose 7.3 percent compared to April and are up nearly 30 percent in the latest 12 months, the report said.
Oil prices -- which collapsed and even turned negative last year -- have recovered as the economy has reopened, and the data showed a 56.2 percent surge compared to May 2020.
That jump reflects so-called "base effects" -- the comparison to very low rates, such as those seen last year -- that Federal Reserve officials say will be "transitory" and fade in the coming months.
In fact, the report said gasoline prices fell 0.7 percent in May compared to the prior month.