In most cases the analysis of DNA mutations in presence of a high excess of wild type DNA fail because of the low sensitivity of the performed method for mutation detection. Here we describe the new high-sensitive and non-radioactive HD-PCR method (for HeteroDuplex-PCR). In opposite to the conventional analytical application the heteroduplex technique is performed to preparatively separate mutated from non-mutated PCR amplified DNA fragments. We used the new method to detect mutations in the tumor suppressor gene APC in stool DNA from patients with sporadic colorectal carcinomas. Since the alteration of the APC gene occurs early in most colorectal tumors, the detection of APC mutations in fecal tumor DNA by HD-PCR may be a powerful tool in non-invasive cancer diagnostics.