The research deals with studying the determinants of spatial variation of ventilation quality and natural lighting in the residential environment of Dekernes city using geographic information systems. The research came to shed light on the effect of urban fabric on natural ventilation levels by studying the general effects on natural ventilation with an analysis of the effect of street characteristics on natural ventilation quality, and also analyzing the effect of urban characteristics and natural ventilation quality from the perspective of urban characteristics. The research aims to monitor the determinants of spatial variation of ventilation quality and natural lighting and its effect on the residential environment in the city.
 
      The study found that the east and west of the city had the highest percentages of compatibility of winds and street directions according to their areas. This was evident in the Mit El-Halouj area, which is located in the southeastern sector of the city, with a percentage of 11.2%, followed by the Manshiyat El-Salam area with about 8.4% in addition to the court complex area, with a percentage of 8.3%, but it reached its lowest in the Sayed Abdel Samad area (the market) with about 4.5%. The Manshiyat Nasser (Kafafi) area was also distinguished by the best natural ventilation with a percentage of 12.2%, in contrast to the Mit El-Rumi area, which decreased due to poor ventilation to reach 2.2%. Natural lighting reached its peak in the Manshiyat El-Salam area, reaching about 12.7% from the perspective of the street direction index, while the Mit El-Rumi area recorded about 3.7%, which indicates the poor state of natural lighting there. The study concluded with the results and recommendations.