Sooybean (Glycine max (l.) Merrill) mechanical harvesting has caused loss of seeds wich are left on the ground. Besids, these damages imposed by combine devices decreased the seed quality during harvesing ans storage. This survey was conducted to determine the soybean harvesting losses and to evaluate the effects of mechanical harvesting on seed viability withing three moisture content levels. After six months storage, the seed quality was evaluated and the infection level of seeds, manually and mechanically harvested, were also compared. The samples were collected in 41 farm throughout Paraná State. The overall results showed that 10.2% of the seeds were left on the ground. The combine header was responsible for 84,8% of those losses; threshing and separating devices for 12% and losses 3.2%. The losses, damages and incidence of microorganisms were significantly higher when the seed moisture cintent was under 11.5%. The lowest loss, seed damage and microorganismsincidence occurred between 11.5% and 14% moisture content. The damages were stastistically higer when the seeds were mechanically harvested. after storage, the quality of mechanically harvested seeds decreased significantly. The fungi biossay tests revealed higher incidence of Fusarium spp., Alternaria spp., and bacteria, unidentified in the mechanically harvested samples. On the other hand, the occurance of Phomopsis sp. and /cercospora Kikichii was higher within harvested samples.