The broadband access provider expects sales to fall about 20 percent from the first quarter.
Company officials said two major customers failed to place anticipated orders in the quarter, meaning the Dallas-based company will post sales of between $100 million to $102 million in the quarter.
The company did not provide any guidance regarding second-quarter profits.
First Call consensus expects Efficient Networks to earn 12 cents a share in the quarter.
"We were disappointed late in the quarter that two major customers did not place significant orders with us as we had anticipated," chairman Mark Floyd said in a prepared release. "While we are dissatisfied with this aspect of our results, we are very pleased with the revenue growth from other customers."
In the year-ago quarter, the company recorded sales of $26.4 million.
Last quarter, Efficient Networks pocketed $6.1 million, or 10 cents a share, on sales of $127.2 million.
The stock moved as high as $186.81 in March before falling to a low of $10.75 in December.
Ten of the 11 analysts following the stock rate it either a "buy" or a "strong buy."