Human mesenchymal stem cells (MSCs) have been isolated from bone marrow and other adult tissues and are potentially useful for tissue engineering. Adipose tissue has several clear advantages as a starting material for harvesting stem cells, as it is abundant and relatively easy to procure. However, existing methods to expand adipose-derived MSCs are less than optimal. Here we describe a new cell culture method that accelerates greatly the growth rate and prolongs the lifespan of adipose MSCs. This was accomplished by using a growth medium with low calcium and supplemented with N-acetyl-L-cysteine and L-ascorbic acid-2-phosphate. Cells produced early in these cultures displayed characteristics similar to those previously reported for multipotential stem cells, including a high frequency of anchorage- independent growth in soft agar, lack of gap junctional intercellular communication in a cell type with serpiginous morphology, and the expression of Oct-4. Furthermore, these cells could readily be induced to differentiate into adipocytes, osteoblasts, and chondrocytes. Thus, modification of growth medium by reduction of calcium and addition of antioxidants greatly enhanced the growth rate and extended the lifespan of adipose-derived multipotential human MSCs.