Capital One Financial Corp., a McLean credit card and consumer lending company, said third-quarter profit increased because of robust growth in its credit card loan portfolios and lower charge-off rates.

Capital One earned $490.2 million ($1.97 a share) in the three months ended Sept. 30, compared with $275.5 million ($1.17) in the same period of 2003. Revenue rose to $2.3 billion from $2.1 billion. Loans on the company's balance sheet on Sept. 30 were $35.2 billion, up from $30.6 billion.

For the first nine months of the year, Capital One earned $1.3 billion ($5.45), compared with $870.2 million ($3.74) in the same period a year earlier. Revenue rose to $6.6 billion from $5.9 billion.

* CoStar Group Inc., a Bethesda-based provider of information services to commercial real estate professionals, credited the continuing rebound in the commercial real estate market for an increase in third-quarter profit.

CoStar said it earned $2.4 million (13 cents per share) for the quarter ended Sept. 30, up from $281,000 (2 cents) for the same period a year earlier. Revenue increased 18.7 percent, to $28.6 million.

Shares of CoStar closed yesterday at $41.60, down $5.11, or almost 11 percent.

* Duratek Inc., a Columbia company that disposes of radioactive materials, earned $9.3 million (63 cents a share) on $77.4 million in revenue in its third quarter, up from $5.3 million (29 cents) on $72.5 million in revenue in the corresponding quarter a year ago.

For the nine months ended Sept. 26, the company earned $18 million ($1.24), up from $11.5 million (77 cents) in the same period last year. Revenue grew to $215.1 million from $213.1 million.

Shares of Duratek closed at $20.14, up $2.65, or 15 percent.

* W.R. Grace & Co., a Columbia-based maker of construction chemicals, building materials and coatings, reported an 11.3 percent increase in third-quarter sales.

The company said it earned $48 million (72 cents a share) on $579.9 million in sales in the quarter ended Sept. 30. That compares with a loss of $9.9 million (15 cents) on $521 million in sales in the same quarter a year earlier.

For the nine months ended Sept. 30, it earned $85 million ($1.29 a share), compared with a loss of $5.7 million (9 cents) in the same period of 2003. Revenue rose to $1.67 billion from$1.47 billion.