Field experiments in the high rainfall zone (HRZ) and the medium rainfall zone (MRZ) in Zambia were designed to determine the natural occurrence of fumonisins (FB(1-2)) in Zambian maize hybrids, accumulation of FB(1-2) resulting from artificial inoculation with Fusarium verticillioides and effects of climate and planting time on FB(1-2) in maize. Combined FB(1-2) concentrations varied from 0 to 13,050 ng/g, with an overall mean of 666 ng/g. Maize from the HRZ had low incidences of FB(1-2)-positive samples (mean 41%) which contained FB(1-2) below 500 ng/g. In the MRZ, higher incidences (mean 97%) and concentrations (40% of samples >1,000 ng/g) were recorded in two out of three years. There was no correlation between mean location FB(1-2) concentrations in individual years and precipitation, number of rain days or monthly precipitation. Postponing the planting time with 10 or 20 days did not significantly affect FB(1-2) concentration, but it reduced the yields in some years.