Ventas Inc. said Friday it is buying the real estate assets of Atria Senior Living Group for $1.5 billion in cash and stock, giving it a portfolio of 118 homes located in wealthy coastal regions.

The health care real estate investment trust is also assuming $1.6 billion in debt.

Ventas said the deal will make the company the largest owner of senior housing communities in the country. The Chicago company owns nearly 600 assets in 44 states.

Under terms of the transaction, Ventas will pay 24.96 million shares, worth about $1.35 billion, and $150 million in cash. It expects the acquired homes to generate about $640 million in revenue next year and to add to its profit in 2012, after transaction costs.

Atria, based in Louisville, Ky., is the country’s fourth largest operator of assisted living properties, with homes in the New York metropolitan area, New England, and California. It is owned by private equity funds managed by Lazard Real Estate Partners.

Before the transaction closes, scheduled for sometime in the first half of 2011, Atria will spin off its management company, which will continue to operate the assets under a management contract with Ventas.

As part of the deal, Atria Chairman Matthew J. Lustig will take a seat on Ventas’ board.

This marks the sixth major deal for Ventas in the last six years.

Earlier this month, the company bought 58 private-pay senior living communities from affiliates of Sunrise Senior Living Inc. for about $41 million.

It also acquired Lillibridge Healthcare Services Inc. in July for $381 million. That purchase included real estate interests in 95 medical office buildings and ambulatory facilities. Lillibridge owns, develops and manages medical office buildings.