In order to evaluate the effect of the mechanical injury caused by processing machines on the seeds of peanut of different sizes, were compared seeds from several machines, generally used in the processing lines of peanut seeds. For comparison were made the tests of purity, germination, first germination counting, speed of emergency and the test of ferric chloride, the latter being included in order to test its viability in peanuts. It was compared, then, the seeds that were manually thrashed with those from the mechanic thrashing-machine, the grader, from the air column, from seed storage bin from specific gravity separator, from seed treater and from sowing-machine. In each machine, seeds of screens 18, 20 and 22 were compared. The obtained results showed that: the higher damages to seeds were caused by thrashing-machine and by sowing-machine. Machine as the grader, the air column and the specific gravity separator, and due to the fact that they eliminate impurities, tend to restore almost completely the initial purity of seed lot. The speed of emergency seems to be little affected by processing machines. Larger seeds showed seedlings with higher weight of dry matter and they stam more intensely by the test of ferric chloride. The test of ferric chloride seems to be not effective to evaluate the mechanical injury caused in the peanuts seeds.