Two Arachis hypogaea L. genotypes (P. I. 337–394F and P. I. 337409) resistant to seed colonization by aflatoxin-producing strains of Aspergillus flavus Lk ex. Fr., were used to study the effects of initial adjusted seed moisture, incubation and storage time, seed maturity, harvest time and seed handling on seed colonization by the fungus. Under conditions highly favorable to the growth of the fungus, seed colonization (P.I. 337394F) was greater at 20% adjusted seed moisture than at 25% seed moisture. Colonization was least at 15 and 30% adjusted moisture. Aspergillus flavus colonized a low percentage (17%) of the cotyledons of P.I. 337409 genotype after 48 hours of incubation, whereas, 100% of the cotyledons of P.I. 331326 (a susceptible genotype) were colonized. Colonization of P.I. 337394F seed with intact seed coats increased with each increase in storage time from 0 to 6 and 12 weeks, and for each increase in temperature from 5 to 20 and 35C. Immature and overmature seed of both resistant genotypes with intact seed coats were more susceptible to colonization than sound-mature seed. However, seed of the resistant genotypes were colonized at a low level, with no difference for seed harvested at 4 successive 2-week intervals, whereas P.I. 331326 had greater colonization for each successive harvest date. Seed coat abrasion, soaking for 5 min. in a H₂SO₄ solution, machine picking or machine-shelling increased colonization of seed over check treatments.