Neurofibromatosis type 1 (NF1) is a dominant hereditary multiorgan disease that causes both benign cutaneous neurofibromas and malignant tumors. Timely detection of malignant transformation in NF1 tumors is of great clinical importance. Also methods to easily monitor individual's overall tumor burden would be useful. Blood plasma is collected from NF1 patients and age- and gender-matched controls. The samples are stored at -80 C until analysis. Free circulating plasma DNA is extracted and quantified using commercial reagents. Also a previously described chemical detection method to observe overall changes in plasma composition is utilized. The analysis results are compared between NF1 patients and healthy controls, and also correlated with NF1 tumor burden and diagnosis of malignancy during five-year follow-up.