The introduction of superior germplasms is essential to the varietal improvement, production and utilization of yam in Taiwan. A total of 90 genotypes including 40 genotypes of Dioscorea alata, 23 of B. alata var. purpurea, 6 of D. esculenta, 5 of D. rotundata, and 1 or D. bulbifera has been collected, propagated, and evaluated by Taiwan Agricultural Research Institute (TARI). The two most productive yam genotypes collected, 70W04 and 70W05, belong to B. alata and exhibited yield potential over 40t/ha. Ten other genotypes (e. g., Tainung No.1) and 4 genotypes (e. g., 70W02) of D. alata also possessed yield potential higher than 30 and 20t/ha, respectively. The average yield performance of D. alata var. purpurea genotypes 70R01 and 70R08 in the field experiment was over 23t/ha. The representative and productive genotypes of other yam species include 71W19 of D. esculenta, 71W14 of D. rotundata, and 71W21 of D. bulbifera with mean yield of 29.4, 22.1, and 25.3t/ha, respectively. Field experiments were conducted for three consecutive years in Taichung area and at three different locations in 1992 to investigate the agronomic and yield performance of genotypes Tainung No.1, 70W04, and 70R01. Both 70W04 and Tainung No.1 had high and stable yield with average tuber yield over 31t/ha. Cultivation at high altitude (600~800 m) showed a more detrimental effect on 70W04 and Tainung No.1 than on 70R01. Despite the easier browning and faster decrease in viscosity, chemical analysis indicated the superior nutritional quality of 70R01 tubers by its higher contents of protein, fat, fiber, total ash, and mineral elements of P. Mg, Fe, and Ca, as compared to the other two genotypes.