<正> It has been developed in this laboratory that a serum-free medium

designated asDMI

is adaptive for long-term culture

freezing and resurgence in liquid nitrogen

and cloningof hybridoma and parental myelomas as well as for cell fusions.In this report

it is describedthat the myeloma cells grown in DMI for more than 3 months maintained their biological charac-teristics such as induction of aseites and subcutaneous somatic tumor in BALB/c mice and toler-ance toward 8-azaguanine

ete..However

the ability of the tumor cells to attach to glass wallwas decreased.The selecting assay of these cells in HAT medium（medium containing hypoxan-thine

aminopterin and thymidine）showed that the death time in DMI was similar to that in theconventional 15％ newborn calf serum-supplemented medium（RPS15）.The hybridoma cellsadapted in DMI secrete monoclonal antibodies in quantities comparable to those produced inRPS15.