Analysts predicted a 6.7 percent increase in the figure, according to a poll by Thomson Reuters.
Revenue at stores open at least a year is a key indicator of a retailer's health because it excludes results from stores recently opened or closed.
Costco reported a 7 percent rise in the metric overseas and a 6 percent gain in the U.S.
Stripping out higher gas prices and the negative impact of foreign currencies, revenue at stores in the U.S. increased 5 percent and climbed 9 percent internationally. For the total company, the figure rose 6 percent.
The wholesale club operator said Thursday that total revenue for the five weeks ended April 1 rose 10 percent to $9.13 billion.
For the year-to-date, revenue at stores open at least a year climbed 8 percent. The figure was up by that same amount in the U.S. and rose 9 percent abroad.
Removing higher gas prices and foreign currencies negative effect, the metric increased 7 percent for the period. In the U.S, the gain was 6 percent, while overseas it was 10 percent.
Total revenue for the period rose 11 percent to $56.34 billion.
In February Costco reported that its fiscal second-quarter profit rose and beat analysts' expectations as its low prices continued to attract shoppers and drive sales.
Costco currently runs 601 warehouses, including 434 in the U.S. and Puerto Rico, 82 in Canada, 32 in Mexico, 22 in the U.K., 13 in Japan, eight in Taiwan, seven in Korea and three in Australia. The Issaquah, Wash. company said that it plans to open up to an additional eight new warehouses before the end of fiscal 2012.