AutoZone Inc. (NYSE: AZO), the largest auto parts retailer in the U.S., released fiscal fourth-quarter financials today that saw earnings rise by a strong 15 percent. The rise in numbers is being attributed to the opening 69 brick and mortar locations in the U.S., 21 new stores in Mexico, and two stores in Brazil. The final tally as of the end of the quarter shows that the company currently has 4,836 stores in 49 states, the District of Columbia and Puerto Rico. There are 362 stores located throughout Mexico and three stores in Brazil. Higher store count translates into higher inventory and in the case of AutoZone, inventory grew by 8.9 percent with per story inventory increasing by 4.8 percent to $550,000 from $525,000 in the same quarter in 2012.

AZO reported a 23.2 percent rise in earnings per share to $10.42 from $8.46 in the year-ago quarter. Net income rose 14.7 percent to $371.2 million, from $323.7 million in last year’s fourth quarter. These calculations take into account the effect of a surplus week in the current quarter, excluding which earnings improved 15.4 percent to $9.76, and net income swelled 7.4 percent to $347.8 million.

Gross profit jumped 12 percent to $1.6 billion (51.8 percent of sales) from $1.4 billion in the year ago quarter. The growth in margins, due to reduction in acquisition costs, was counterweighted by the company’s acquisition of AutoAnything, an online auto parts and accessories retailer. AZO acquired the e-commerce company to leverage its less than spectacular online business.

Operating profit climbed 13.6 percent to $636.2, from $560.1 million in the fourth quarter of 2012. Operating expenses increased 11 percent to $968.2 million, or 31.3 percent of sales, versus $872.3 million, or 31.6 percent of sales, a year ago. The slight decrease in operating expenses was again due to the influence of the additional week in the quarter.

AZO was sitting on cash and cash equivalents of $142.2 million as, up from $103.1 million as of the end of August 2012. Total debt was reported at $4.19 billion, compared with $3.77 billion in the same quarter in 2012.

Also of note, AutoZone repurchased 1.3 million shares during the quarter for $560 million, signifying an average price of $428 per share. The company had $468 million worth of shares remaining for repurchase at the close of the fourth quarter.

Shares are trading up today by 0.53 percent on news of the earnings report on light volume.

Disclosure: The author has no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.