There was no aflatoxin contamination of cottonseed originating from non-damaged bolls or non-damaged locks from insect-damaged bolls in samples from fields that had not been weathered. In contrast, 61% of seed from insect-damaged locks had high (i.e. >20 ppb) aflatoxin concentrations, with an average concentration of 649 ppb. Cottonseed samples from modules originating from fields that had not been weathered showed a similar association of high aflatoxin concentration with insect injury. High concentrations (35-2,500 ppb) of aflatoxin were found in seed associated with bright green-yellow fluorescent (BGYF) lint, which indicates Aspergillus flavus infection occurred prior to boll maturity. High concentrations (27-2,200 ppb) were also found in seed associated with insect-damaged, non-BGYF lint. Concentrations in seed following exposure of mature cotton in the field to rain showers over a period of four weeks were high in both insect-damaged (930-1,400 ppb) and non-damaged (150-280 ppb) locks. Aflatoxin was present in 3% of non-damaged seed obtained from modules made from non-weathered cotton and it was present in 82% of similar samples made from weathered cotton (average content 760 ppb). This study shows that in the absence of weathering, insect injury is the main factor associated with aflatoxin contamination in south Texas.