On the basis of this study, IgA was best preserved in frozen human milk by thawing either overnight in the refrigerator or under warm running water. If either of those procedures are to be used, it is suggested that bacterial monitoring should be performed. Because current technology does not allow for accurate low internal temperature monitoring of liquids, it is concluded that use of the microwave oven for the treatment of human milk is inappropriate. However, because microwaving is as effective as holder pasteurization in killing bacteria, and because it would be less expensive and is faster, this process should be further investigated.