First-quarter revenue at Insperity Inc. (NYSE: NSP), a provider of professional employer organization services, rose 11.0 percent year-over-year to $595.2 million as the average number of worksite employees rose 8.5 percent.

Houston-based Insperity reported an average of 121,938 worksite employees paid per month in the first quarter, up from 112,409 in the year-ago quarter. Revenue per worksite employee rose to $1,627 per month in the first quarter from $1,591 in the same period last year.

Insperity’s first-quarter gross margin rose to 17.3 percent from 17.0 percent in the year-ago quarter.

Net income at the PEO services firm rose in the first quarter to $13.9 million, up 58.0 percent from $9.0 million a year ago.

Insperity Inc. (NYSE: NSP)
For the first quarter ended March 31, 2012, compared with the same period last year.
Revenue: $595.2 million, +11.0 percent
Net income: $13.9 million, +58.0 percent