What happened Share of online travel giant Priceline Group (NASDAQ: PCLN) tumbled on Wednesday despite a strong second-quarter report. Priceline's guidance seems to be the culprit, with the company calling for a slowdown in travel bookings and earnings below analyst expectations. As of 12:36 p.m. EDT, the stock was down 7.3%. So what Priceline reported second-quarter revenue of $3.02 billion, up 18.3% year over year and $30 million higher than the average analyst estimate. Gross travel bookings were $20.8 billion, up 16% year over year, and up 19% adjusted for currency. The company booked 170 million room nights during the quarter, up 21% year over year, while airline ticket bookings fell 8.7% to 1.8 million. Image source: Priceline Group. Non-GAAP EPS came in at $15.14, up 20% from the prior-year period and $0.94 above analyst expectations. Higher operating costs were more than offset by revenue growth and an improved gross margin. "We are pleased with the performance of the business and will continue to build our franchise by adding properties to the platform and by investing in technology, customer experience and content expansion," said Priceline CEO Glenn Fogel. While Priceline's results beat expectations, the company's guidance wasn't quite as rosy. Priceline expects total gross travel bookings to grow by 9% to 14% year over year adjusted for currency during the third quarter, a significant slowdown compared to the second quarter. Non-GAAP EPS is expected between $32.40 and $34.10, below the average analyst estimate of $34.14. Now what Shares of Priceline have surged in recent years, up more than 200% over the past five years, and up more than 2,000% over the past 10 years. The stock is far from cheap as a result of that surge, trading for around 44 times 2016 GAAP earnings. The company's strong growth justifies a premium valuation, but an outlook calling for a slowdown in growth has investors putting on the brakes. 10 stocks we like better than Priceline GroupWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the 10 best stocks for investors to buy right now... and Priceline Group wasn't one of them! That's right -- they think these 10 stocks are even better buys. Click here to learn about these picks! *Stock Advisor returns as of August 1, 2017Timothy Green has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Priceline Group. The Motley Fool has a disclosure policy.