Masimo Corporation (MASI)

Masimo Corporation developed and manufactured noninvasive patient monitoring technologies and was headquartered in Irvine, California. The company was founded in 1989 by Joe Kiani and became known for Signal Extraction Technology (SET), a pulse oximetry approach designed to measure oxygen saturation reliably during patient motion and low blood flow. That technology became the base of a broader range of monitors and sensors sold worldwide.

Beyond SET pulse oximetry, Masimo offered rainbow measurements for hemoglobin species and related parameters, SedLine brain function monitoring, capnography and gas monitoring, regional oximetry, and hospital automation and connectivity software such as Patient SafetyNet. Its customers included hospitals, emergency medical services, home care and long-term care providers, and physician offices, served through direct sales, distributors and original equipment manufacturer partnerships. The company also sold consumer health products, including wearables.

Masimo went public in August 2007, listing on Nasdaq under the symbol MASI. For many years it was involved in extensive patent litigation, including a prolonged dispute with Apple over pulse oximetry features in the Apple Watch. In 2022, Masimo acquired Sound United, a consumer audio group with brands including Bowers & Wilkins, Denon and Marantz, a move that drew investor criticism. The company later sold its consumer audio business to Harman International in 2025.

Governance also changed substantially. In 2024, a proxy contest led shareholders to elect directors nominated by an activist investor, and Joe Kiani departed the company's leadership. A new management team was installed and concentrated Masimo on its core healthcare monitoring business and on resolving legal matters.

On February 17, 2026, Masimo announced a definitive agreement under which Danaher Corporation would acquire it for $180.00 per share in cash, an enterprise transaction valued at approximately $9.9 billion. Danaher described the purchase as strengthening its diagnostics business, which also encompasses acute care diagnostics, and said Masimo would operate under its own brand as a stand-alone company within the Diagnostics segment.

Danaher announced completion of the acquisition on June 10, 2026, with Masimo becoming a wholly owned subsidiary. Masimo common stock ceased trading on Nasdaq upon closing and a Form 25 was filed with the SEC to remove the shares from listing and registration. Former Masimo shareholders received the cash merger consideration under the terms of the merger agreement. The transaction ended Masimo's nearly two decades as an independent public company and marked one of the larger medical technology acquisitions announced in recent years. Because the consideration was entirely cash, Masimo shareholders did not receive any Danaher shares.