Professional employer organization revenue at Automatic Data Processing Inc. (NYSE: ADP) rose 13.7% year-over-year to $283.4 million in its fiscal second quarter ended Dec. 31, 2008, the company reported today.

ADP said the average number of worksite employees in its PEO services program rose 13% to 193,000 in the quarter.

The company said it expects PEO revenue growth of between 14% and 15% for the full fiscal year.

Total second-quarter revenue for ADP was $2.20 billion, up 2.5% from the same period in the previous fiscal year.