Underground pit structures are commonly employed by farmers for on farm storage of yam (Dioscorea spp) in Nigeria and other parts of developing world. This traditional storage structure is used without provision for adequate air exchange or ventilation. This study investigated the performance of yams stored in underground pit structures provided with air vents. Three experimental pits of similar dimensions were constructed with Pit 1 installed with one PVC vent; Pit 2 had two PVC vents and Pit 3 without vent which served as control. 20 Kg weight of yams was loaded in each pit measuring 1.0 m in diameter and 0.65 m in depth. The results of the study show that a lowest temperature range of 30-38ºC was maintained in pit 1 (improved) temperature range of 34-40ºC in Pit 2 (semi-improved) while temperature in pit 3 range from 36- 42ºC. The relative humidity obtained were 84, 76 and 70% in pit 1, 2 and 3 respectively. The sprouting indexes obtained within 8 weeks storage period were 46.2, 53.8 and 76.9 for pit 1, 2 and 3, respectively. The cumulative weight loss obtained in pit 1, 2 and 3 were 44.8, 69.5 and 79.2%, respectively for the 8 weeks storage period. Increased in storage period for yams is possible with adequate ventilation in underground pit structure.