Walgreen's (NYSE:WAG) sales data showed a healthy May, but investors may have expected something closer to April's stellar showing and nudged shares down in recent trading. Meanwhile, has the company lost some of its luster now that rival CVS (NYSE:CVS) has received FTC approval to buy Eckerd from J.C. Penney (NYSE:JCP)?

Same-store sales at Walgreen were up 8.5% in May, with overall sales increasing 12.8% to $3.18 billion. However, compare that to last month, when Walgreen reported a same-store sales hike of 10.3%, with total sales up 14.9% and pharmacy sales higher by 17.2% overall.

One might imagine that springtime staples like suntan oil, bug spray, and allergy meds drove consumers to drugstore chains in May, but the picture here is mixed. Walgreen's pharmacy sales increased 14%, while comparable pharmacy sales rose 10.5%. The company's "front-end" sales rose 5.3%, a tad lower than April's 5.6% number.

Walgreen, of course, has been the No. 1 drugstore chain for some time now, with CVS doing its darnedest to nip at its heels. The latter company's planned purchase of Eckerd -- approved by the FTC yesterday -- will put CVS at the top of the heap in terms of its number of stores, and CVS's addition of Eckerd will put it close to Walgreen in annual sales as well.

Many people don't see third-place Rite Aid (NYSE:RAD) as much of a threat to anybody. However, with CVS encroaching on Walgreen's territory through its new Eckerd chain, it could add up to some heated rivalry -- if CVS knocks Eckerd into tip-top shape. Or could it? On the Walgreen discussion board here at the Fool, some investors have kicked around the issue, and many believe that Walgreen is too formidable an enemy for CVS to beat at its own game.

Today, Walgreen shares lost a little more than 1% in recent trading. Maybe investors are a little spooked by a May that seemed mellow by comparison to April. Maybe it's the specter of CVS making Eckerd a contender in Walgreen territory. At any rate, trading at 27 times forward earnings, Walgreen currently sounds a bit rich to buy in.

What do you think? Can CVS get Eckerd into shape and take on Walgreen? Talk it over with other Fools on the Walgreen discussion board.

Alyce Lomax does not own shares of any of the companies mentioned.