On Assignment Inc.’s (NASD: ASGN) second-quarter revenue jumped 97.1 percent year over year with its acquisition in May of Apex Systems, which ranked on both the lists of largest U.S. information technology staffing firms and fastest-growing staffing firms. Excluding Apex, On Assignment’s existing business posted a 28.2 percent increase in second-quarter revenue.

Apex added $99.0 million to On Assignment’s revenue during the second quarter. Year-over-year second-quarter revenue increases in other business units at Calabasas, Calif.-based On Assignment include:

• Oxford, IT and engineering staffing, revenue rose 34.9 percent to $88.1 million.
• Physician staffing revenue rose 47.3 percent to $25.0 million. Revenue in this segment was positively impacted by the company’s acquisition of Healthcare Partners in 2011.
• Allied healthcare revenue rose 25.6 percent to $13.7 million.
• Nurse travel revenue rose 55.5 percent to $16.8 million. On Assignment reported the quarter included $5.3 million in revenue related to supporting an existing customer that had a labor disruption. The same quarter last year recorded just $900,000 in labor disruption revenue
• Life sciences revenue rose 2.2 percent to $40.5 million.

Second-quarter gross margin narrowed to 31.4 percent from 34.0 percent a year ago. The nurse travel segment posted the largest increase in gross margin, rising to 26.3 percent from 24.2 percent in the year-ago quarter.

Net income jumped 45.2 percent on a year-over-year basis to $8.5 million.

On Assignment Inc. (NASD: ASGN)
 For the second quarter ended June 30, 2012, compared with the year-ago quarter.
 Revenue: $283.2 million, +97.1 percent
 Net income: $8.5 million, +45.2 percent