The study was conducted to do preliminary review of geology and water quality at Sg Serai hot spring, Hulu Langat, Selangor, Malaysia. Langat River basin can be divided into 3 distinct zones. The first can be referred to as the mountainous zone of the northeast corner of Hulu Langat district. The second zone is the hilly area characterised by gentle slopes spreading widely from north to the east in the middle part of Langat basin. The third zone is a relatively flat alluvial plane located in the southwest of Langat Basin. Water samples, SSP2 and SSW2 are polluted, with an anomalously high reading of fluoride. Fluorosis has been described as an endemic disease of tropical climates, but this is not entirely the case. Waters with high fluoride concentrations occur in large and extensive geographical belts associated with a) sediments of marine origin in mountainous areas, b) volcanic rocks and c) granitic and gneissic rocks; resulting the high concentration of fluoride in water samples.