This Week's ETF Winners & Losers

Exchange-traded funds tracking basic materials were among the best performers of May's first full week following Monday's bid for a potential blockbuster deal between two major industrial concerns.

As the week started, Pittsburgh-based aluminum giant Alcoa (AA Quote) said it was launching an effort to buy Canada's Alcan (AL Quote) for $27 billion. Alcoa jumped 6.8%, and Alcan surged more than 31%.

The Ultra Basic Materials ProShares (UYM Quote) ETF added 3.7% to $87. The iShares Dow Jones U.S. Basic Materials (IYM Quote) ETF was higher by 1.7% at $68.93. The Materials Select Sector SPDR (XLB Quote) gained 1% to $39.78.

Semiconductor-related ETFs were also among the winners of the week, thanks to positive earnings news out of Nvidia (NVDA Quote) Thursday. Excluding items, the company earned 42 cents a share, comfortably ahead of the Thomson Financial target. The chipmaker also offered a positive second-quarter forecast, and the stock rose 4.2% for the week.

The Ultra Semiconductor ProShares (USD Quote) ETF climbed 2.5% at $82.89. The Semiconductor HOLDRs (SMH Quote) added 1.3% to $37.98. The SPDR S&P Semiconductor (XSD Quote) ETF gained 1% to $53.39, and the iShares Goldman Sachs Semiconductor (IGW Quote) ETF ended higher by 0.8% at $66.16.

On the losing side, the HealthShares Emerging Cancer (HHJ Quote) ETF was the week's largest decliner. Holding Dendreon (DNDN Quote) plummeted 68.5%, most of that after the Food and Drug Administration said it required more test data for the company's drug Provenge.

The HealthShares Emerging Cancer ETF finished the week lower by 16.2% to $22.54.

Gold-related ETFs also declined for the five sessions. Futures ended down 2.5% at $672.30 an ounce. The streetTRACKS Gold Shares (GLD Quote) ETF eased 2.5% to end the week at $66.48. The iShares Comex Gold Trust (IAU Quote) closed down 2.5% to $66.52, and the Market Vectors Gold Miners (GDX Quote) ETF slipped 1.9% to $39.92.

Elsewhere, ETFs tracking silver were among the worst performers. Silver futures fell 1.7% over the five days to close at $13.30 an ounce. The iShares Silver Trust (SLV Quote) slid 1.8% to $131.47. The PowerShares DB Silver (DBS Quote) ETF shed 1.7% to $26.04.