Good day, ladies and gentlemen and welcome to the Benchmark Electronics First Quarter 2018 Earnings Conference Call. At this time, all participants are in a listen-only mode. Later we will conduct a question-and-answer session and instructions will be given at that time. (Operator Instructions) As a reminder, this call is being recorded.
I would now like to introduce your host for today's conference Lisa Weeks, Vice President of Strategy and Investor Relations. Please go ahead, ma'am.
Thank you, Christie and thanks everyone for joining us today for Benchmark's first quarter 2018 earnings call.With me this afternoon, I have Paul Tufano, CEO and President and Roop Lakkaraju, CFO. Paul will provide introductory comments and Roop will provide a detailed review of our first quarter financial results and second quarter outlook. We will conclude our call with a Q&A session.
After the market closed today, we issued an earnings release highlighting our financial performance for the first quarter of 2018 and we have prepared a presentation that we will reference on this call. The press release and presentation are available online under the Investor Relations section of our website at www.bench.com. This call is being webcast live and a replay will be available online following the call.
Please take a moment to review the forward-looking statements advised on Slide 2 in the presentation. During our call, we will discuss forward-looking information. As a reminder, any of today's remarks that are not statements of historical facts are forward-looking statements, which involve risks and uncertainties described in our press releases and SEC filings. Actual results may differ materially from these statements and Benchmark undertakes no obligation to update any forward-looking statements. The Company has provided a reconciliation of our GAAP to non-GAAP measures in the earnings release as well as in the appendix of the presentation.
I will now turn the call over to our CEO, Paul Tufano.
Paul J. Tufano
Thank you, Lisa and good afternoon ladies and gentlemen.
If you could please turn to Slide 4, I would characterize Q1 as the solid quarter for Benchmark. We met actually exceeded our commitments on both revenue and EPS. The revenue was $608 million for the quarter up 9% year-over-year. We had good growth across the majority of our segments. Gross margin was 9.5%, 40 basis point improvement year-over-year and non-GAAP operating income was 3.7% or 10 basis point year-over-year improvement.
EPS on a non-GAAP is $0.41, $0.09 year-over-year. And our cash cycle days were 16 at the low end of our target range. Operating cash flow was $45 million and our ROIC was 11.2%, a 230 basis point growth from the year ago period.
If you turn to Page 5, we are making good progress on bookings. As you all know, revenue growth is critical for us to achieve our long-term financial model and bookings are critical to what we were. In the second quarter, we generated $171 million of bookings. And of those bookings, 63% were in our higher value markets and 37% in traditional markets.