Five pathogenic fungi (Alternaria alternata, Bipolaris sorokiniana, B. spicifera, Fusarium avenaceum and F. graminearum) were evaluated for seed discoloration, shriveling, germination and seedling vigor of wheat. Three wheat cultivars (Yecora Rojo, Logame and Sammah), two inoculation times (at anthesis and 12 days later) and two environmental conditions (wet and dry) were used in this investigation. Considerable differences were recorded between the tested fungi for seed discoloration, shriveling, germination and seedling vigor at each treatment. Fungal mycelia were also assessed in wheat grains via estimation of chitin and ergosterol contents. For each fungal species, significant differences between samples were detected. It is evident that visual characteristics of seed provide an imperfect guide to the extent that seed is infected by fungi. Chemical analysis for either chitin or ergosterol, if developed for routine use, could well be helpful in identifying potentially samples on which additional analyses for specific mycotoxins could be carried out.