Ameritech, Inc. v. American Information Technologies Corp.

Ameritech (plaintiff), a small Ohio company, had used the unregistered "Ameritech" name and mark exclusively since 1979; AIT (defendant), a large Chicago telecommunications company entering new markets, adopted the same name in 1983 through a national ad campaign, and Ameritech sued for likelihood of confusion after the district court found no such likelihood and granted AIT summary judgment.

Whether a senior user of a mark can bring a trademark infringement claim for likelihood of confusion if a junior user's widespread use of a similar mark leads consumers to assume the two companies are somehow connected or that the senior user's products originate from the junior user.