Recently Nuclear Malaysia completed the development of chronic irradiation facility called Gamma Green House, and has started using this facility in the present mutation breeding programme. Chronic irradiation is an exposure to ionizing radiation over a long period (weeks or months), depending on the nature and sensitivity of the irradiated plants (Azhar et al., 2009). Previous studies on chronic gamma irradiation have found that chronic irradiation is very useful in minimizing radiation damage, and can induce a few improved characters on irradiated plants at the same time (Okamura, 2008). To date, several potential mutant lines of Hibiscus rosa-sinensis with different flower colours have been identified and they will be propagated further up to the fourth generation (M1V4) to confirm the stability of the traits.