The transaction includes $215 million in cash and $20 million in MindSpring stock.
The deal gives the company Netcom's approximately 400,000 individual Internet access accounts, 3,000 dedicated Internet access accounts, and 18,000 Web hosting accounts in the United States.
"This acquisition is consistent with our mission to become a major player in the telecommunications industry of the future," MindSpring CEO Charles Brewer said in a statement.
In the past year, MindSpring has been on a buying spree, snapping up rival ISPs. In November, it bought the subscriber base of cable company Cox Interactive. Earlier it acquired rival Sprynet for between $35 million and $40 million from parent company America Online.
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Axxel Institutional Equity Services initiated coverage of MindSpring today with a "strong buy" rating after the acquisition was announced.
The sale also includes various ICG assets used in serving those subscribers, including leased operations facilities in San Jose, California and Dallas.
MindSpring also acquires all U.S. rights held by ICG to the "Netcom" name, as well as select software and equipment. The Netcom operations in Canada and the United Kingdom, however, are not included in this transaction.
ICG plans to sell the remaining international assets of its Netcom subsidiary and said it will announce the result of those efforts at a later date.
MindSpring hopes that the acquisition will put the company into the big league, with more than 1 million dial-up subscribers.
For ICG, an integrated communications provider, the sales represents a move to concentrate on its core telecommunications business.
"This sale and the related network services agreement with MindSpring is consistent with our business plan to focus on our core telecommunications operations, and expand our customer base by building stronger relationships with Internet service providers," said ICG CEO J. Shelby Bryan.
ICG merged with Netcom On-Line Communication Services in January 1998 for about $285 million, and said that the underlying data network was an integral reason for its acquisition.
"Our retention of these assets greatly complements our regional markets and our initiatives to deliver wholesale ISP network services," Bryan added.
The transaction is expected to be completed later this quarter, subject to certain customary closing conditions and regulatory approvals.