Arsenic contamination of terrestrial environments has occurred globally as a result of anthropogenic activities. Remediation of heavy metal contaminated soil is an expensive process, and awareness of different factors controlling the levels of risk is needed to improve risk assessments and inform remediation efforts. The residence time of contaminants in soil or ‘ageing’ (e.g. metals and metalloids) is a factor which generally influences the bioavailability and toxicity of soil-borne contaminants. Despite As being an important terrestrial contaminant, the effect of As ageing on phytotoxicity has received relatively little research. To assess the influence of ageing on As phytotoxicity, a standard test was conducted to compare the growth rate of Cucumis sativus L. (cucumber) in with contaminated soil aged for up to 5 years. Nine different soils with different characteristics were collected from different states of Australia. Soils were spiked with different concentrations of As to induce a dose-response curve. Soils were incubated under aerobic conditions for 0.25 yr for the first As toxicity test and 5 yr for the second test. Cucumber plants were grown for 28 days in both experiments and effective As concentration that inhibits cucumber growth by 10%, and 50% were compared to calculate the impact of ageing on As phytotoxicity. Ageing for 5 yr significantly reduced As phytotoxicity relative to soils aged for 0.25 yr by 1.4 to 2.7 fold when expressed on a total As basis. In one soil there was no increase in EC50 values from ageing from 0.25 to 5 yr. For the dataset as a whole, ageing from between 0.25 and 5 yr increased the EC50 values by 1.6 fold. The relatively limited influence of ageing between the two periods of the current study may indicate that the first three months are most influential for the ageing of soil-borne As.