Take your pick of zoological metaphors to describe the strong first quarter for heavy-equipment maker Caterpillar (NYSE:CAT). Want to say that it's come out of its cocoon? Want to say that the Cat finally showed its claws? Whatever you pick, don't forget to add a "well done," too.

Sales for the quarter were up 29% to $8.34 billion -- a performance that trounced the $7.3 billion Wall Street consens-a-guess and was well above even the high estimate of $8.13 million. Sales were boosted by higher pricing, as well as higher volumes in the machinery and engine businesses and some beneficial foreign exchange translations.

Sales in the machinery business were up 30%, and all geographical regions (North America, Latin America, Europe, Asia/Pacific) showed double-digit growth. Strength was fueled not only by the robust construction market but also by strong demand from the mining sector.

In the engines business, total revenue climbed 29%, with double-digit growth everywhere except in Latin America. Here, too, sales were strong across the board in such markets as on-highway truck engines, petroleum engines (used for compression, drilling, and well servicing), marine engines, and engines for the electrical power market.

While gross profit actually dipped slightly from last year, total operating margins improved slightly, and the company posted growth in operating profit of 33%. Better performance in the engines group was a major help here; the 29% increase in revenue translated into more than triple the level of operating profits ($183 million vs. $41 million) a year ago.

The company reported much better operating cash flow for the quarter (positive $179 million) and eked out $6 million in free cash flow. If that figure sounds unimpressive, I'd caution investors not to place too much influence on quarter-to-quarter moves in FCF.

No doubt, then, these are great days for Cat. The housing business is booming, and mining and energy companies finally have the budgetary flexibility to update and replace their machinery. What's more, the passage of a federal highway bill could free up additional funds for even more of the heavy machinery and engines that make up Cat's specialty.

Based on an outlook for 3.5% world economic growth and continued strength in housing, mining, transport, and the marine sector, Cat is looking for revenue growth between 16% and 18% in 2005.

With a P/E fairly below the trend of the past five or so years, it might be fair to wonder whether Cat is at or near its own cyclical peak. Just as in the torrid housing construction, mining, and energy markets, the good times can't roll on forever. So although Cat might make sense for investors looking to play this maturing boom theme, I don't think anyone should expect this kind of growth to continue indefinitely.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).