This thesis investigated thermal comfort for naturally ventilated housing in Iran with special reference to Ilam. An important aim was to establish the neutral temperature and the acceptable range of environmental conditions for Dam people in their houses. The methodology used for this aIm was field studies. These studies were divided into two parts- one in the hot season and the other in the cool season. The results showed a good relationship between neutral temperature and mean indoor temperature and also between outdoor temperature and neutral temperature. The indoor comfort temperature (Tn), which is dependent on outdoor temperature (Tom), could be found from the following equation: Tn = 17.3 + 0.36 Tom The findings of the study revealed that the Ilam people could achieve comfort at higher indoor air temperatures compared with the recommendations by international standards like ISO 7730. The results also showed that passive systems as a main comfort strategy could be applied to housing design in Ilam. By using the results of this study, strategies to minimise housing energy consumption, not only for Ilam but also for other regions, which have similar climates and cultures to Ilam, can be proposed.