Thidiazuron (TDZ) has been used as an additive to tissue culture medium which stimulates organogenesis. TDZ is a growth hormone traditionally classified as a cytokinin, but which also exhibits some properties representative of auxins. The optimally effective concentration of TDZ in callus culture media has yet to be defined for many species, but usually ranges from 3-12 μmol in those species which have been evaluated. TDZ has proven effective in many leguminous crops, and it is therefore predicted that it will also ameliorate organogenesis in Trifolium pratense, (red clover). The embryogenic response of NEWRC red clover germplasm using Gamborg's B5 basal media protocol was evaluated in a factorial arrangement of treatments. One hundred forty NEWRC seeds were scarified and germinated in darkness, each meristem was divided six times, and two explants were transferred to each a 0, 1, and 10 μmol TDZ callus induction media. These were allowed to develop for four weeks and were rated by callus condition. Subsequently, these calli were divided into three pieces again and transferred to 0, 1, 10 μmol embryo development media. Eight weeks after initiation, samples were again rated for callus quality, quantity and number of developing embryos. These were then transferred without division to a rooting media with no TDZ. Results collected twelve weeks after initiation show that callus quantity is best when the samples were exposed to no TDZ during callus induction, and 10 μmol during embryo development. The number of shoots was highest in those samples treated with no TDZ in the callus induction stage and 1 μmol TDZ during the embryo development stage. Results showed that callus quality is best in the absence of TDZ.