Jawbone is suing rival fitness technology firm Fitbit, accusing it of stealing commercially sensitive data.
The lawsuit accuses Fitbit of poaching staff, stealing intellectual property and confidential trade data.
Former Jawbone staff used USB storage devices to take data to Fitbit, the San Francisco lawsuit alleges.
Fitbit says it is "unaware" of any confidential information from Jawbone in its possession and will "vigorously" defend itself against the allegations.
In a statement Fitbit also said: "As the pioneer and leader in the connected health and fitness market, Fitbit has no need to take information from Jawbone or any other company."
Earlier this month Fitbit, which makes wearable devices that record health data, launched its first share sale in which it hopes to raise $100m (£65m).
The company plans to list shares on the New York Stock Exchange.
Fitbit reported sales of almost $340m in the first quarter of this year, triple the same period in 2014.
Jawbone's lawsuit names Fitbit and five former Jawbone employees. Jawbone also believes 10 other former staff were involved.
The case says that a recruiter from Fitbit contacted 30% of Jawbone's staff. Both companies are based in San Francisco.
Jawbone is seeking compensation wants to prevent former employees from disclosing any other commercially sensitive information.