Concentrations of Natural Occurring Radioactive Material (NORM) and terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. An attempt was made to statistically predict and validate environmental gamma radiation dose rates based on limited number of actual field measurements using sodium iodide (NaI(Tl)) detector. Statistical analysis including the correlations between the actual and predicted dose were made based on 32 different lithology and soil type combinations. Results of field measurements, have shown that more than 50% of the predicted data were not significantly different from the actual measured data. The interpolation method in GIS was used to produce an isodose map based on the prediction equation. A correlation of multiple regression on the predicted versus lithology and soils dose rates gave relationships of DP = 0.35 DL + 0.82 DS – 0.02, r2 = 0.736. A predicted isodose map was subsequently plotted base on 4 dose rates classes, ranging from 0.1 – 0.3 μSvhr-1.