GAAP operating expenses for third quarter 2018 were $69.4 million, or 21.6 percent of revenue, and $65.0 million, or 20.3 percent of revenue, on a non-GAAP basis, which excluded $4.4 million of amortization of acquisition-related intangible asset expenses. GAAP operating expenses in the third quarter 2017 were $72.6 million, or 25.5 percent of revenue, and in the second quarter 2018 were $69.4 million, or 22.8 percent of revenue.

Third quarter 2018 GAAP net income was a record $30.9 million, or $0.61 per diluted share, compared to net income of $14.5 million, or $0.29 per diluted share, in third quarter 2017 and net income of $25.1 million, or $0.49 per diluted share, in second quarter 2018.

Third quarter 2018 non-GAAP adjusted net income was a record $34.5 million, or $0.68 per diluted share, which excluded, net of tax, $3.6 million of non-cash acquisition-related intangible asset amortization costs. This compares to non-GAAP adjusted net income of $22.6 million, or $0.45 per diluted share, in the third quarter 2017 and $29.3 million, or $0.58 per diluted share, in the second quarter 2018.

The following is an unaudited summary reconciliation of GAAP net income to non-GAAP adjusted net income and per share data, net of tax (in thousands, except per share data):