A novel methodology to identify L1 Ta-1 insertion events in human patient tissue samples using high-throughput pyrosequencing was developed. Using this method, many new L1 Ta-1 insertions were identified. One novel L1 Ta-1 insertion was identified in a tumor tissue DNA, but was absent in the adjacent normal tissue DNA. These results suggest that L1 Ta-1 insertions can occur during colon cancer development, where they may contribute mutations conferring a selective advantage to the developing tumor.