In a sign of Google’s major ambitions in the health care industry, t he search giant is working with the country’s second-largest hospital system to store and analyze the data of millions of patients in an effort to improve medical services, the two organizations announced on Monday.

The partnership between Google and the medical system, Ascension, could have huge reach. Ascension operates 150 hospitals in 20 states and the District of Columbia. Under the arrangement, the data of all Ascension patients could eventually be uploaded to Google’s cloud computing platform.

It is legal for health systems to share patients’ medical information with business partners like electronic medical record companies. Even so, many patients may not trust Google, which has paid multiple fines for violating privacy laws, with their personal medical details.

Google mentioned the arrangement in an earnings call in July, but provided few details. More about the arrangement was announced on Monday, after The Wall Street Journal published an article about it.