Background: Worldwide, indoor radon exposure is considered to be the second leading cause of lung cancer, particularly among people who stay indoors for a long time as the children and the elderly. The goal of this study is to get a better understanding of indoor radon levels in the houses of the Gaza governorate. Materials and Methods: One hundred eighty passive diffusion radon dosimeters containing CR-39 solid state nuclear track detectors (SSNTD) were distributed in the rooms of the Gaza governorates houses following a cluster random sampling. Only 154 dosimeters were found in the places and collected, while the remaining 26 dosimeters were lost. The detectors were left for two months during the period from March to June of 2006. Variability between dwellings neighborhoods, floors, rooms at the same floor, ventilation status, smoking, dwelling age were assessed. Results: The indoor radon concentrations in the houses of Gaza governorate were lower than the EPA and ICRP recommended limits (150 Bq/m3), with a mean indoor radon concentration (mean±SD) of 40±14 Bq/m3 and a range from 3 to 105 Bq/m3. The house ventilation status was the key variable which affects the indoor radon level, since badly ventilated houses had higher indoor radon concentrations, particularly in the basement floors rather than the higher floors. Conclusion: Despite fulfilling the international limits, we strongly recommend conducting a wider national survey for natural radiation measurements and mapping radon-borne areas throughout the country. Moreover, well ventilation of the house indoor environment is highly recommended.