The Internet is increasingly becoming a place where people look up phone numbers and addresses and track down old friends, rather than going to the pay directory services of the telephone companies. These look-up sites are becoming important spots for advertising as millions of people visit them.

Topping the busy list: Infospace.com, which 4.3 million different people stopped into in June, according to Nielsen/NetRatings, which tracks Internet usage.

The sites draw on public databases and ask users to volunteer information about themselves, which is added to the data on tap. The sites offer premium look-up services as well to supplement their advertising revenue. Infospace.com, for instance, offers to search public records for such information as property ownership and professional licenses.

WHERE'S WHOEVER?

The most popular people finders on the Web in June:

Rank, site: 1. infospace.com

No. of unique visitors: 4.26 million

Reach*: 6.72%

Rank, site: 2. people.yahoo.com

No. of unique visitors: 2.09 million

Reach*: 3.3

Rank, site: 3. switchboard.com

No. of unique visitors: 1.39 million

Reach*: 2.2

Rank, site: 4. anywho.com

No. of unique visitors: 756,006

Reach*: 1.19

Rank, site: 5. whowhere.lycos.com

No. of unique visitors: 740,005

Reach*: 1.17

Rank, site: 6. 1800ussearch.com

No. of unique visitors: 610,000

Reach*: 0.96

*Percent of total Internet audience reached.

SOURCE: Nielsen/NetRatings