There were 128 chief executive officers who left their jobs in July, outplacement firm Challenger, Gray & Christmas said.
That figure is 36 percent higher than June's 94 departures, 54.2 percent higher than July 2012 and the highest since February 2010 when CEO departures reached 132.
July's departures pushed the year's total to 729, 5.3 percent higher than the first seven months of 2012.
The employment firm said healthcare companies -- a category that includes diagnostic manufacturers, some software firms and hospitals -- notched 34 CEO departures in July, half of which were from hospitals or healthcare systems.
Government and non-profit corporations posted the second highest departures for July with 20. Financial firms followed with 19 CEO departures.
"Some companies saw their fiscal year come to an end on June 30," CEO John Challenger said.
"So, it is not unusual to see some volatility as organizations reassess leadership and make changes," he said.
CEOs also reassess. The most common reason for CEO departures in July was retirement, which was followed by executives stepping down, sometimes to stay with the organization as chairman of the board.
Fourteen other CEOs found jobs at other companies, Challenger, Gray & Christmas said.