The distribuition of contaminated carrot seeds is an important way of disseminating Alternaria dauci, A. radicina and A. alternata. This research was carried out in order to determine when the carrot seeds are infected (or contaminated) and for how long they can remain as a source of inoculum. During the anthesis, thirty primary umbels and thirty secondary umbels were tagged at random. Every week, during six weeks, five umbels of each type were collected. Four hundred seeds from each type of umbels and from each date of harverst were analised through the blotter test; for this, the seeds were incubated under 25ºC and a day lenght of 12 hours, for seven days. For the determination of the survival, the seeds were kept under environmental conditions. Seed samples were taken monthly, from january 1996 to january 1997, and analised through the blotter test. The association of Alternaria spp. with the carrot seeds was already detected in the first sample, that is, the one harvested at the 7th day after anthesis. The three species of Alternaria survived was shown by Alternaria dauci, followed by A. alternata. The detection of A. radicina was higher in the low levels of the other two species.