With one exception, March was a pretty unspectacular month for the three big-box retailers. The delayed arrival of the Easter Bunny was blamed for the lackluster results. The lone standout, Motley Fool Stock Advisor pick Costco (NASDAQ:COST), seemed to be unaffected by the shift in Easter's arrival from March to April. It reported a 7% increase in comps, easily exceeding its rivals' performance. Target (NYSE:TGT) increased its comps by 2.2%, while Wal-Mart (NYSE:WMT) once again brought up the rear with a 1.4% gain.

Just like last month, Target had the toughest road, since it had to improve upon 8.2% growth in the year-ago quarter. Costco's strong month is even more impressive, when you consider that it was following its own 7% increase in the year-ago period. Wal-Mart, the world's biggest retailer, continued its slow and steady growth, posting a 4.3% gain in the year-ago quarter.

As the table below shows, this marks the eighth consecutive month that Costco has led the way. It reported an 8% gain in February, while Target and Wal-Mart were struggling to keep pace with 3.6% and 3.2% growth, respectively.

9/05

10/05

11/05

12/05

1/06

2/06

3/06

Costco

11

10

6

7

9

8

7

Target

5.6

5.7

2.6

4.7

5.2

3.6

2.2

Wal-Mart

3.8

4.3

4.4

2.2

4.7

3.2

1.4


Looking ahead to next month, Target and Wal-Mart expect to give Costco a better fight. Both are feeling confident about posting strong numbers, particularly Target, which is predicting comps growth of 9% to 11% in April. Wal-Mart also hopes to have one of its best recent performances, predicting a same-store sales increase of 4% to 6%.

Based on comps data, Costco is clearly the frontrunner of this trio. However, Foolish investors know there are a plethora of other measures that must be taken into account before making a purchase. I like this segment and each of these companies, but not at any price. Do your Foolish research and determine whether any of them deserve to be a part of your portfolio.

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Fool contributor Mike Cianciolo owns shares of Wal-Mart, but holds no financial position in any other company mentioned in this article. The Fool has a disclosure policy.