A laboratory investigation entitled “Standardization of pretreatment and drying method for white onion (Allium cepa)” was conducted at post harvest technology laboratory, Department of Horticulture, College of Agriculture, Dr. B.S. Konkan Krishi Vidyapeeth, Dapoli during the year 2009-2010. It consisted of five pretreatments i.e. dipping in 2% alum solution, 2% salt solution, 0.25% KMS solution, 0.1% KMS+2 % CaCl2 solution and control (T5) with three drying methods i.e. sun drying, oven drying and solar drying. Thus, in all fifteen treatment combinations replicated thrice in factorial randomized block design. Pretreated and dried white onion slices were stored in 400 guage polyethylene bag for 6 months at ambient temperature for further study in relation to chemical parameters, rehydration ratio and sensory evaluation. The chemical parameters under study were significantly varied during storage with different pretreatments, drying methods and their interactions and decreasing trend was observed except reducing and total sugars. Among drying methods, solar drying noticed comparatively better retention of reducing and non-reducing sugars, protein and also rehydration ratio as well as sensory score. Oven dried samples showed better retention of T.S.S. and ash only. Among different pretreatments, 0.25%KMS and 0.1%KMS+2%CaCl2 were found comparatively better for retention of T.S.S., non-reducing and total sugars and ascorbic acid. The sensory score was comparatively more in 0.25%KMS and 0.1%KMS+2%CaCl2 pretreated samples. With regards to interaction effects 0.25 per cent KMS pretreated samples followed by solar drying showed better results in most of the chemical parameters including sensory score. Thus, the pretreatments 0.25 % KMS as well as 0.1 % KMS+2 % CaCl2 followed by solar drying were found to be suitable for dehydration of white onion.