Treated effluent was used in irrigation of field crops at Berka and Gabal Al Asfar sites. Nine and seven wells were installed at Gabal Al Asfar and Berka respectively in order to investigate the impact of using treated effluent on groundwater quality. The groundwater at Gabal El Asfar was notably less polluted than at El Berka, despite the long period of sewage irrigation on this site. There were larger concentrations of nutrients that would probably be derived form sewage irrigation, but all of the other parameters measured were similar to, or less than, those found at El Berka. Heavy metal concentrations in the groundwater of both sites were similar and small. This is despite the elevated concentrations of heavy metals which have accumulated in Gabal El Asfar from long-term sewage irrigation, but these data demonstrate that heavy metals are not generally susceptible to leaching when applied to soil but are strongly bound, thus leading to accumulation in top soil. Groundwater samples were examined for the presence of pathogenic bacteria (salmonella), faecal coliform bacteria and helminth ova. The results indicate that the groundwater of both sites are contaminated by sewage, although it is highly unlikely that this was a direct result of effluent irrigation to the trials considering soil type and depths to groundwater.