Abstract: Solanum aculeastrum is a medicinal plant used by the traditional healers of the Eastern Cape of South Africa, for the treatment of cancers. The antiproliferative activities of this plant were studied in vitro using three human tumour cell lines (HeLa, MCF7 and HT29). Methanolic extracts of the fruits had the highest antiproliferative activity with IC50 between 17.1 and 41.9 μg mL-1 while the activities of their aqueous extracts ranged between 27.9 and 48.5 μg mL-1. The leaf extracts had no anticancer activity under the experimental conditions tested. Overall, the HeLa and MCF7 cell lines were much more sensitive to both extracts than HT29 cells.