Soybean seeds of the cultivar ?IAC 11? were subjected to the following factors of deterioration: mechanical damage (combined harvesting), delayed harvest (1, 2, 3 and 4 weeks afler harvesting maturity), drying at 40°C, 45°C and 50°C for 4 hours and storage under non controlled environmental conditions for 3, 6 and 9 months. The evaluation of the effects was conducted through the standard germination test, using seeds treated or not with Thiram. The counting was made 5 days afler the beginning of the test. The paper towel used as substratum received an amount of water twice its dry weght. Each treatment was repeated 8 times. According with the results it was verified that speciflc causes of seed deterioration lead to the development of specific symptons (signs or abnormalities) and that most of the times a source of deterioration is characterized by more than one type of symptom. Seedlings exhibiting broken or fractured cotyledons were considered to tipify mechanical damage as a source of seed deterioration. Drying as a source of seed deterioration was characterized by a large occurrence of seedlings in which the tip of the primary root showed a brownish color. Deterioration from storage resulted in a high proportion of seedlings with hypocotyls showing granular lesions and cotyledon with less than half its surface covered by darkened areas.