Selling, general and administrative expenses were $86.5 million, up from $84.2 million in the first quarter of 2013. The sequential increase in expense was primarily due to higher incentive compensation related to the sequential growth in gross profit and headcount additions to drive growth.
Amortization of intangible assets was $5.3 million, up from $3.9 million in the second quarter of 2012. This increase related to the timing of the acquisition of Apex Systems, which was acquired in the middle of the second quarter of 2012. Consequently, the second quarter of 2012 included amortization expense for only half the quarter.
Interest expense for the quarter was $4.2 million compared with $4.0 million in the second quarter of 2012. Interest expense was comprised of interest on the credit facility of $3.8 million and amortization of capitalized loan costs of $0.4 million.
Write-off of loan costs totaled $15.0 million ($9.2 million, $0.17 per diluted share, after tax) and related to the refinancing of the credit facility in May. This refinancing was treated as an early extinguishment of debt, which resulted in a full write-off of all capitalized loan costs associated with the old facility. Under the new $500 million credit facility, the interest rate on the term B loan was reduced 150 basis points and the interest rate on the revolver and term A loan was reduced 75 to 125 basis points, depending on the leverage ratio.Adjusted EBITDA (earnings before interest, taxes, depreciation, and amortization of identifiable intangible assets plus equity-based compensation expense, impairment charges, acquisition-related costs and fees and expenses of the outside consulting firm assisting with our strategic planning initiatives), was $44.2 million, up from $38.4 million for the second quarter of 2012 on a pro forma basis. The Adjusted EBITDA margin (Adjusted EBITDA as a percentage of revenues) was 10.6 percent.