NEW YORK — The nation's largest Internet service providers all say they haven't partnered with Silicon Valley startup NebuAd Inc. to monitor Web surfing and deliver targeted advertising to their subscribers. Here is a look at six smaller service providers, however, that have conducted trials. The companies say all the tests have ended, often to review privacy and related issues. No provider is known to be currently using NebuAd.

Bresnan Communications LLC

Bresnan's test involved about 6,000 customers in and around Billings, Mont., from April 1 to June 26. The company notified customers by sending e-mails to customers' Bresnan addresses and posting notices on its site. Customers were given an opportunity to decline, or opt out, of targeting, and 18 people took advantage of that option.

Cable One Inc.

Cable One, a unit of The Washington Post Co., conducted a test in Anniston, Ala., with about 14,000 customers for six months starting Nov. 20. The company did not provide specific notice of the trial, nor did it let customers opt out of participation. It said tests are routinely conducted and fall under general notices and agreements posted on the company's Web site and mailed to subscribers annually. The company said it would have sought affirmative consent, known as opt in, had it continued with full deployment.

CenturyTel Inc.

CenturyTel's trial had 20,000 customers, mostly in and around Kalispell, Mont. The trial ran from November to June. The company sent e-mail notifications of an updated privacy policy, to which a paragraph on NebuAd was added. The company said 82 subscribers opted out during the trial. Before suspending a broader launch, CenturyTel started informing customers of it via e-mail and bill inserts.

Embarq Corp.

The nation's fourth-largest traditional phone company, Embarq conducted a test this year with 26,000 subscribers in the Gardner, Kan., area. The company did not directly inform customers of the test but included a general notice within its privacy policy posted online. The company said 15 people opted out.

Knology Inc.

Knology's trial covered an unknown number of customers in West Point, Columbus and Augusta, Ga.; Panama City, Fla.; Knoxville, Tenn.; and Huntsville, Ala. Tests began in West Point in January and expanded until the company stopped all trials on July 14. The company says customers were informed through a service agreement posted on its Web site, and subscribers who happened to see it had a chance to opt out of participation. The company did not say how many did.

WideOpenWest

From early March until July 8, WOW used NebuAd's system on its 330,000 customers in its entire service area, which covers Cleveland and Columbus, Ohio, Evansville, Ind., Chicago and Detroit. Besides Web postings, WOW notified customers after the fact via e-mail and physical mail and reminded them on billing statements to review privacy notices online. The company said it received 3,355 opt outs, though an unknown number came from the same customer.