Armstrong back on top, 15 seconds late

Lance Armstrong (Astana) returned to cycling's heights with the San Martino di Castrozza climb at the Giro d'Italia, where he finished 15 seconds behind winner Danilo Di Luca. It was Armstrong's first mountaintop finish in nearly four years, since then teammate George Hincapie won on the Pla-d'Adet in the 2005 Tour de France.

"I am happy with my performance today," Armstrong said. "This was my first big climb since retiring. I had a good feeling and no collarbone pain at all."

A derailleur problem on the final 13.75-kilometre climb forced the 37-year-old out the back of the lead group. The mechanical issue saw Armstrong lose time to teammate Levi Leipheimer and eventual stage winner Di Luca (LPR Brakes).

"Of course, it was not a very difficult climb," said Armstrong. "For Di Luca it was a perfect finish with the gradual climb. Ivan Basso, Di Luca, Stefano Garzelli and Damiano Cunego all looked very good."

Armstrong retired from the sport following his seventh Tour de France win in 2005. He returned last year and announced he would race the Giro d'Italia three-week stage race shortly after, but a fractured collarbone in April's Castilla y León nearly derailed his plans.

Armstrong's collarbone failed to prevent him from staying with the favourites in the Giro d'Italia's fourth stage, in Northern Italy. He led with Yaroslav Popovych and Janez Brajkovic over the Croce d'Aune and onto the day's final climb of San Martino.

"Tomorrow will be a better indication," he added. "It will be a long and hard day. We'll see. I don't know what to expect."

Stage five's main challenge is the 24.9-kilometre Alpe di Siusi. It comes at the end of a 125-kilometre day and is the second of two Dolomiti stages in the opening week of the Giro d'Italia.