New issues in U.S. corporate bond markets topped $29 billion last week, with refinancing making up a significant portion of the mix.

American Tower (AMT -0.59%) issued $1.8 billion in a private placement spread over five- and 10-year tranches. The company is using the money to repay debt.

Avon (AVP) showed up at the market's door with four issues with maturities ranging from three to 30 years totaling $1.5 billion. The money is being used to repay a number of different notes.

Canadian insurance-provider ACE Limited (CB 0.76%) wrote $950 million between 10- and 30-year notes through its ACE INA Holdings subsidiary. ACE is using the money to redeem paper that's maturing in 2014 and 2015. Today's low rates will save ACE about $20 million per year in debt service costs. It's curious that ACE decided to lock in the rates now, rather than wait a year or two for the existing paper to mature.

Medical supplies and health care technology company McKesson (MCK -1.35%) delivered $900 million in new debt split between five- and 10-year notes. The company is using the money to pay off a bridge loan used in its PSS World Medical acquisition.

Mattel (MAT 0.67%) wasn't playing around with five- and 10-year notes totally $500 million. The money will go toward repaying $450 million of maturing notes. Today's lower rates will cut Mattel's debt service expenses by about $10 million per year. Any money left after the payoffs will go toward general corporate purposes.

Specialty insurer Markel issued 10- and 30-year paper totaling $500 million. The "use of proceeds" section of the SEC filing cited the ever-uninformative "general corporate purposes." There is an interesting kicker, however. Markel says "the offering is not condition upon the completion of the acquisition of Alterra." But if the Alterra acquisition isn't completed by Nov. 1, Markel must redeem the bonds at 101% of face value. Fortunately for Markel, Alterra's shareholders recently approved the acquisition.

Historically low rates continue to save companies money when they roll over maturing debt, lower the cost of financing acquisitions, and lower the cost of capital for growth, research and developing, marketing, and other "general corporate purposes."