Dow Chemical Co. on Thursday reported it lost $37 million in the fourth quarter in part because of weak demand and lower operating rates.

``This has been one of the most challenging quarters that Dow has ever faced,'' said Michael D. Parker, president and chief executive.

The huge chemical company said its loss amounted to 4 cents a share for the three months ended Dec. 31 in contrast to a profit of $149 million, or 16 cents a share, a year ago.

Excluding charges, including those related to Dow Chemical's merger with Danbury, Conn.-based Union Carbide, the Midland-based company reported a loss of 1 cent a share.

The consensus forecast of analysts surveyed by Thomson Financial/First Call was earnings of 5 cents per share.

Net sales in the quarter were $6.35 billion, down 12 percent from $7.23 billion in the year ago period.

For the full year 2001, Dow lost $385 million, or 43 cents per share, compared with earnings of $1.68 billion, or $1.85 per share, in 2000.

Sales for the year totaled $27.81 billion, down 6 percent compared with $29.53 billion during 2000.

``The chemical industry has been, and is, facing the worst business environment in decades,'' Parker said. ``At the same time, Dow has had the added challenge of integrating Union Carbide and other strategic acquisitions.''

Dow's merger with Union Carbide was completed Feb. 6, making it the world's second-largest chemical company behind DuPont Co. Parker said the company is ahead of schedule in integrating Union Carbide's operations.

``As business conditions improve, the benefit of this work will be further leveraged and will significantly impact the bottom line,'' Parker said.