This paper analyzes the use and effectiveness of gamma radiation, in order to decontaminate and protect cultural heritage. Fungi are widely spread in the environment, ergo they pose the risk to many works of art, and biodegradation is inevitable, unless the proper care is taken of these artefacts. Also, the natural contamination of the material has been analyzed, colonies were identified microscopically, following gamma radiation of the samples. Samples were divided into two groups. One group was exposed to the conditions of elevated humidity (Rw=70-80%, t=25°C), and the other group did not undergo any treatment, those samples remained in dry conditions. Both groups were irradiated with subsequent radiation doses 2,7,20 and 50 kGy, which were administered with two different velocities of 0,1Gy/s and 9,8 Gy/s. The effectiveness of the method was evaluated in correspondence with colony growth after the certain time, i.e. 0th, 7th, 14th and 28th day after irradiation has taken the place. Natural contaminants have shown radio resistance due to given results, because there has been noticed colony growth in samples, which were treated with a high dose of radiation. The dose of the matter is several times higher than dose, which is usually used for decontamination purpose. Growth of other fungal species has been noticed too. Due to dot contamination, it is very difficult to conclude how effective fungicide gamma radiation actually is.