Propolis, commonly known as bee glue, is a resinous substance of complex mixture of several compounds collected by honeybees from trees and leaf buds and has been known for several pharmacological activities. The effect of propolis on onion root tip cells was investigated with a view to assess its anti-mitotic effects. Propolis caused inhibition in onion roots growth in a dose-dependent manner. A decrease in mitotic index and an increase in the chromosomal aberrations were observed in propolis treated root tips which may indicate its genotoxic effect on plant cells. The level of reduced glutathione (GSH) in the root tips was significantly decreased after propolis treatment and this may lead to decrease the protective ability in the cells thereby enhancing the development of chromosomal abnormalities.