Irradiation of the K-rasLA1 mouse model with a fractionated dose of 1.0Gy 56Fe- particles increases the incidence of invasive carcinoma compared to unirradiated controls or those irradiated with an acute dose. Microarray profiling was perfromed on whole lungs from K-rasLA1 mice in order to determine global expression changes in the lung following radiation exposure. RNA was extracted from K-rasLA1 lungs from unirradiated control animals or those irradiated with a fractionated or acute dose of 1.0Gy 56Fe- particles 70 days post-irradiation when lungs are still histologically indistiguishable and only contain benign lesions. 129S2 K-rasLA1 mice were either irradiated with an acute (1.0Gy x1; n = 15) or fractionated (0.2Gy x5; n=13) dose of 1.0Gy 56Fe- particles or left unirradiated (n=13). Animals were euthanized 70 days post-irradiation and RNA was extracted from the whole left lung of each animal.