Shares of casual apparel retailer American Eagle (NASDAQ:AEOS) were off slightly in morning trading today, but that's after a solid gain in yesterday's session following the morning release of upbeat March sales numbers and fiscal first-quarter earnings guidance.

American Eagle said yesterday that March "month-to-date" same-store sales were ahead 7.8% year over year, as American Eagle stores improved 7.9% and the Bluenotes Canadian denim operation rose 5.7%. Total revenues were up nearly 18% from 2003's figures.

All this is much better than last year's March period, in which consolidated sales rose less than 2%, and total same-store sales fell nearly 9%. (The chain has 918 stores, up from 868 a year ago.) Last year's quarter got off to a bad start across the board, but this year, the company is reporting solid sales growth companywide, as well as strong margins and reduced markdown activity.

That's no doubt what's driving the earnings upgrade: American Eagle is now pointing investors toward first-quarter EPS of $0.25 to $0.30, well ahead of last year's $0.09 even as the company's share count will have increased slightly since the 2003 report. Strong February sales were an early tip-off.

Investors have to like the improvement American Eagle has shown over the last 12 months. The company has a youthful and appealing mix of fashions displayed on its website and seems well positioned for the warm-weather months. That said, many investors have already voted with their dollars: American Eagle holders, as well as those of casual cousins Abercrombie & Fitch (NYSE:ANF) and Gap (NYSE:GPS), have all seen their shares leap since mid-December.

Talk about the remarkable rise in this company's shares on our American Eagle discussion board.

Fool contributor Dave Marino-Nachison doesn't own any of the companies in this story.