ffymetrix and Oxford Gene Technology have settled all their litigation concerning patents on the gene chip, one of the fundamental inventions in biotechnology, the companies said.

Terms of the settlement were not disclosed in the announcement of the accord late Friday. But Affymetrix is expected to make a filing with the Securities and Exchange Commission today indicating that it is taking a one-time charge to earnings, an executive said.

Gene chips, also called DNA chips or microarrays, are pieces of glass or other material containing thousands of genes or gene fragments. The chips are widely used to test which genes are active in a particular cell. For instance, determining which genes are turned on in tumor cells but not in healthy cells could provide valuable clues to how cancer arises.

Affymetrix has dominated the gene chip business, helped in part by a strong patent portfolio. But it is facing new competition from companies like Motorola , Corning and Agilent Technologies , the spinoff from the Hewlett-Packard Company .

Oxford, a tiny British company, also claims some fundamental patents based on the work of Edwin Southern, an Oxford University professor who is the company's majority owner. While Oxford does not yet sell its own gene chips, it has licensed its technology to Agilent and to Incyte Genomics . Oxford and Affymetrix have been battling each other in courts in the United States and Europe.

In November, a jury in a Delaware federal court ruled that Affymetrix had infringed an Oxford patent. It was reported at the time that Oxford was seeking $40 million in damages.

But shortly before that verdict, Affymetrix had won a ruling in a separate case in Britain saying it had legally acquired rights to Oxford's patents in 1999 by buying a business that had a license to those patents.

Under the settlement announced Friday, the Delaware case will be dropped. Oxford will also give up its appeal of the British decision, effectively giving Affymetrix the rights to use Oxford patents. Both companies also will drop efforts to invalidate the other's patents.

The companies said that it was best to put the litigation behind them to concentrate on their businesses. Oxford has said it wanted to break up what it has described as Affymetrix's patent stranglehold on the gene chip business, which Oxford claims has kept prices high for the chips and limited their use.

But it is not clear what effect this settlement will have on the gene chip business. Andrew W. Millar, head of operations at Oxford, declined to comment. In a statement, Professor Southern said, "It is essential for genomic research that these matters have been resolved and that O.G.T. can concentrate on its main objectives of developing its own technology and business and licensing others to do the same."