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Aflatoxins are carcinogenic toxins that frequently contaminate maize and groundnut.  <i>Aspergillus</i> <i>flavus, A. parasiticus</i> and two unnamed taxa have been implicated as causal agents of aflatoxin contamination in Africa. Improved understanding of etiology in Zambia may facilitate aflatoxin management. Maize (n=225) and groundnut (n=137) samples from three agroecologies of Zambia were examined from 2012 to 2014. Fungi were isolated and assigned to morphological species with <i>A. parasiticus</i> the most common followed by <i>A. flavus</i> L strain and fungi with S strain morphology. Crop aflatoxin content was quantified with lateral flow immunochromatographic assays. Agroecozone One had the highest proportion of unfit (>10 ppb) groundnuts and maize (56% & 20%, respectively). To investigate potential for safe crops to become contaminated in storage, crop samples (5 g) were incubated without inoculation (31⁰C, 100% RH, 7 days) and the aflatoxin content quantified with fluorescence densitometry after thin layer chromatography. Aflatoxins increased (p<0.05) in 70% (n=61) of the crops; 60% (n=37) increased to above 10,000 ppb. Greater increases occurred in groundnuts than maize. The most common species in groundnut was also the species that produced the highest average concentrations of aflatoxins in sterilized maize, <i>A. parasiticus</i> (40% and 22% of section Flavi in groundnut and maize, respectively). Etiology of contamination in Zambia is complex with several causal agents.