MEMPHIS, Tenn., Sept. 25, 2013 (GLOBE NEWSWIRE) -- AutoZone, Inc. (NYSE:AZO) today reported net sales of $3.1 billion for its fourth quarter (17 weeks) ended August 31, 2013, an increase of 12.0% from the fourth quarter of fiscal 2012 (16 weeks). Excluding sales from the additional week included in this year's quarter, sales were up 5.6%. Domestic same store sales, or sales for stores open at least one year, increased 1.0% for the quarter. Net income for the quarter increased $47.5 million, or 14.7%, over the same period last year to $371.2 million, while diluted earnings per share increased 23.2% to $10.42 per share from $8.46 per share in the year-ago quarter. Excluding the additional week, net income for the quarter increased 7.4% over the previous year's quarter to $347.8 million, while diluted earnings per share increased 15.4% to $9.76 per share. For the quarter, gross profit, as a percentage of sales, was 51.8% (versus 51.8% for last year's quarter). While flat for the quarter, lower acquisition costs led to gross margin enhancements which were offset in part by the inclusion of the recent acquisition of AutoAnything (40 bps). Operating expenses, as a percentage of sales, were 31.3% (versus 31.6% last year). The decrease in operating expenses, as a percentage of sales, was due to leverage gained on the 17 th week of sales. For the fiscal year ended August 31, 2013, sales were $9.1 billion, an increase of 6.3% from the prior year, while domestic same store sales were flat for the year. Operating profit increased 8.9% on an operating margin of 19.4%. For fiscal 2013, net income increased 9.3% to $1.0 billion, while diluted earnings per share for the period increased 18.3% to $27.79 from $23.48. Excluding results from the additional week, sales increased 4.3% from the prior year, and operating profit increased 6.4% on an operating margin of 19.3%. Net income, excluding the extra week, increased 6.7% to $993.1 million, and diluted earnings per share increased 15.6% to $27.15. Return on invested capital was 32.7%, while full year cash flow before share repurchases and changes in debt was $1.0 billion.