Digital PCR (Dig-PCR) is a method that converts the exponential nature of PCR into a linear signal for detecting mutations in a small fraction of a cell population. The technique involves isolating single molecules, amplifying them individually, and then using fluorescent probes to detect mutations. This approach allows for a reliable and quantitative measure of variant sequences in a DNA sample. The method was demonstrated by detecting a mutant ras oncogene in the stool of colorectal cancer patients. The study highlights the importance of detecting somatic mutations, which are now recognized as primary causes of cancer. Traditional methods for mutation detection, such as DNA sequencing and restriction enzyme analysis, have limitations in sensitivity and quantification. Dig-PCR overcomes these limitations by amplifying individual template molecules, resulting in homogeneous PCR products that can be easily distinguished using fluorescent probes. The process involves diluting DNA samples so that each well contains an average of one template molecule, followed by PCR amplification. Fluorescent probes, such as molecular beacons, are used to detect mutant and wild-type sequences. The results show that Dig-PCR can detect mutations at very low frequencies, as demonstrated by the detection of mutant c-Ki-Ras genes in stool samples from colorectal cancer patients. The method has broad applications in both clinical and research settings, including the detection of cancer cells in bodily fluids and the analysis of rare mutations. The technique is also applicable to RNA samples, allowing for the quantification of gene expression levels. The study emphasizes the potential of Dig-PCR for improving the detection of mutations in clinical diagnostics and for advancing research into cancer genetics.Digital PCR (Dig-PCR) is a method that converts the exponential nature of PCR into a linear signal for detecting mutations in a small fraction of a cell population. The technique involves isolating single molecules, amplifying them individually, and then using fluorescent probes to detect mutations. This approach allows for a reliable and quantitative measure of variant sequences in a DNA sample. The method was demonstrated by detecting a mutant ras oncogene in the stool of colorectal cancer patients. The study highlights the importance of detecting somatic mutations, which are now recognized as primary causes of cancer. Traditional methods for mutation detection, such as DNA sequencing and restriction enzyme analysis, have limitations in sensitivity and quantification. Dig-PCR overcomes these limitations by amplifying individual template molecules, resulting in homogeneous PCR products that can be easily distinguished using fluorescent probes. The process involves diluting DNA samples so that each well contains an average of one template molecule, followed by PCR amplification. Fluorescent probes, such as molecular beacons, are used to detect mutant and wild-type sequences. The results show that Dig-PCR can detect mutations at very low frequencies, as demonstrated by the detection of mutant c-Ki-Ras genes in stool samples from colorectal cancer patients. The method has broad applications in both clinical and research settings, including the detection of cancer cells in bodily fluids and the analysis of rare mutations. The technique is also applicable to RNA samples, allowing for the quantification of gene expression levels. The study emphasizes the potential of Dig-PCR for improving the detection of mutations in clinical diagnostics and for advancing research into cancer genetics.