I'd now like to turn the call over to Steve Anderson who has a few comments before we begin.
Before we get started, I would like to point out that there will be a replay of this conference call available via the telephone and Internet. Please refer to today's press release for replay information. This morning, the company filed a Form 8-K that included additional information on our business and operations. This information is also available on our website. Analysts and investors are directed to this 8-K and our website to review this supplemental information.
Additionally, we refer you to today's press release, which is available on our website, for a reconciliation of non-GAAP financial measures discussed during today's call to GAAP. These non-GAAP measures include adjusted EPS, adjusted EPS excluding amortization, free cash flow, and adjusted operating income. I would also like to point out that we are making forward-looking statements during this conference call.
These forward-looking statements include, among others, statements about our expected financial results, the implementation of our business strategy and the ongoing benefits from the Genzyme Genetics and other acquisitions. These statements are based upon current expectations and are subject to change based upon various factors that could affect the company's financial results. Some of these factors are set forth in detail in our 2011 10-K and subsequent filings. The company has no obligation to provide any updates to these forward-looking statements even if our expectations change.
Now, Brad Hayes will review our financial results.
William B. Hayes
Thank you, Steve. On today's call, I will review 4 key measures of our financial performance: Cash flow, revenue growth, margin and liquidity. I'll also review our 2012 guidance.
First cash flow. Our cash flow remain strong. Free cash flow for the trailing 12 months ended March 31, 2012 was $686.9 million. We remain pleased with our cash collections. DSO was 48 days at the end of March, an increase of 1 day year-over-year and 2 days sequentially. During the quarter, we reduced our bad debt rate to 4.4%.