Abstract: A six weeks trial was conducted to evaluate the effectof hardness of two underground waters on production of broiler reared at Poultry Experiment Station (PES), TandoJam and Mubashir Farm, Rahuki. Two equal groups of chickens in age and weight were reared under similar managemental conditions and offered same feed (iso-nitrogenous and iso-caloric) ad libitum during June-July, 2002. A non-significant intake of water and significant feed intake was recorded in group B (11.711 and 5.303) as compared to group A (11.587 and 5.083) lit/kg per broiler. Significant increase in the mean live bodyweight was recorded in group A (2.224) as compared to group B (1.851) kg b-1 and produced carcass weight in group B (3.17 and 18.33) gm b-1 as compared with group A. (2.15 and 12.10) gm b-1, respectively. Spleen and kidney sizzes were larger in group B (2.32 and 6.58) than A (1.58 and 3.99) cm b-1, respectively enhanced live body weight/weight gain and dressed carcass recoveries. Spleen and kidney weights and sizes increased with the increase in hardness of water.