The present work had for objective to evaluate the effect of the osmotic conditioning, with and without treatment with fungicide, in the plysiologic and sanitary quality of two onion lots (Allium cepa L.), cultivar AG-558, group Baia Periforme. Osmotic conditioning was made using solution of polyethylene glycol (PEG 6000), with water potential of -0.75MPa, and 15°C, during 120 hours. The used fungicides were Iprodione+Thiram 0.2% (200g.i.a./100kg of seeds), Captan 1.25% e Metalaxyl 0.62%. For the comparison it was used as control the seeds not conditioned with and without treatment with fungicide. The seeds were appraised for the first count and final count of the germination test; radicle length; emergence speed and the final emergence in sand seedbed and for the sanitary test, being used the method of the paper-filter. The entirely randomized experimental design was used, with four replicates, being the comparison among averages done by the Duncan test, the 5% of probability. The osmotic conditioning stimulated the development of mushrrooms associated to the seed, and the inclusion of the fungicides iprodione and thiram provided the control of these microorganisms and maintained the germination levels and the vigor of the seeds of the two studied lots. The osmotic conditioning seeds, treated or not with fungicide iprodione and thiram, metalaxyl or captan, they presented larger speed and emergency percentage.