Advantages and disadvantages of in vitro and mouse ascites methods for producing mAb are highlighted in this section. It should be noted that it is likely that in vitro methods will meet more than 90% of the needs for mAb. Some of the advantages and disadvantages are concerned with animal-welfare issues. Others deal with the economics of producing mAb. As noted below under the section titled “In Vivo and In Vitro Methods for Commercial Production of mAb”, in vitro methods can cost ½ to 6 times the mouse ascites method. Some of the factors that cause in vitro production to be expensive are labor and equipment costs that are usually due to poor hybridoma production of mAb in vitro. If the investigator must use several types of media or different equipment, as happens occasionally, labor costs rise and research is delayed (Moro and others 1994; Stoll and others 1996b; Butler and Huzel 1995).