New numbers released Monday by DataQuick show May home sales were down 18 percent from a year ago.
Foreclosures accounted for 33.4 percent of last month's sales, down slightly from 33.8 percent in April and 33.9 percent a year earlier.
Last year, homebuyers were taking advantage of federal tax credits that were about to expire.
Home prices also are lower in every Southern California county.
In Los Angeles County, the median price fell 7 percent in a year to $320,000.
Orange County dropped 6 percent to $425,000.
Ventura County's median price was $360,500, down 5 percent.
Riverside County fell to $197,000 and San Bernardino County fell to $150,000, both down 6 percent in a year.
The Associated Press contributed to this story.