New data suggest that foreclosures are rising in more expensive housing markets.

About 30% of foreclosures in June involved homes in the top third of local housing values, up from 16% when the foreclosure crisis began three years ago, according to new data from real-estate Web site Zillow.com. The bottom one-third of housing markets, by home value, now account for 35% of foreclosures, down from 55% in 2006.

The...