Although most cases of lung cancer are associated with tobacco smoking, many lung cancers occur in non-smokers. The causes of lung carcinoma in non-smokers remain mysterious, but cancer-causing viruses are among possible causes. We plan to use a new method to identify disease-causing microbes, computational subtraction, to look for viruses that cause bronchoalveolar carcinoma. This sub-type of lung cancer occurs most frequently in people who have never smoked, compared to other lung cancer types. We will take bronchoalveolar cancer tissue and make libraries that represent the genes in the cancer tissue. We will then determine the sequence of DNA in those genes. This means that we will read the order of each nucleotide or "letter" in the DNA and find the exact DNA "words" that are written in the cancer tissue. We will then compare these sequences to the sequence of the human genome. DNA sequences from viruses are unlikely to match the human sequence. If we find such sequences, we can test whether possible viruses are specifically present in multiple cases of bronchoalveolar carcinoma.