A novel microchip electrophoresis instrument based on single-photon avalanche diodes was used for the molecular characterization of mutations in disease genes. The identification of the main mutation causing cystic fibrosis, named DeltaF508, by the Amplification Refractory Mutation System was used to validate the technology. In our implemented protocol the wild-type and mutant allele-specific primers are labeled with Cy5 and Cy5.5, respectively. The protocol enables the amplification of the DNA sample in a single PCR. The genotype was deduced from the fluorescence of the amplicons run in the CE microchip. Validation on 15 DNA samples from either homozygous wild-type or heterozygous and homozygous mutated control subjects proved the complete reliability of the system, thus confirming its high diagnostic potential.