Stocks Stage Impressive Rally

Primus Telecom(PRTL Quote) shares slumped $2.97, or 26.3%, to $8.34 following the company's disappointing fourth-quarter results announced after the bell Thursday.

Shares of Electronic Data Services(EDS Quote) fell $1.39, or 6%, to $21.90 after its weak earnings report.

In Friday research, Prudential upgraded shares of Bed Bath & Beyond(BBBY Quote) to overweight from neutral, and UBS upgraded shares of Monsanto(MON Quote) to buy from neutral. Bed Bath & Beyond shares gained $1.27, or 3.1%, to $42.08, and Monsanto rallied $1.98, or 6.5%, to $32.29.

Looking ahead, earnings season continues next week, with approximately 25% of the S&P 500 left to report. Monday's calendar is very light, however.

In economics, wholesale inventories is the only major release scheduled for Monday and is forecasted to grow 0.3% in December, a slight deceleration from 0.5% in the month prior.