AbstractTwo alternative electrophoretic strategies were used to study the internal variation of the HRAS1 minisatellite after minisatellite variant repeat mapping (MVR‐PCR) was carried out. While the use of automated sequencers with fluorescent based technology is ideal for analyzing fragment size, and therefore, for analyzing the repeat number, the use of polyacrylamide gels and silver staining is more appropriate for the analysis of internal variation. Thirteen different fragments ranging from 27 to 80 repeats were found in a sample from 80 healthy Caucasian individuals. By using MVR mapping we were able to detect heterozygotes which appear as homozygotes when fragment length analysis was used. As a result of this, the 13 alleles, which we had detected, increased to 16 alleles when MVR sequences were analyzed. The extremely conservative arrays of repeats allow us to infer the theoretical origin of rare alleles from a major group of specific alleles. The HRAS1 minisatellite has been extensively studied due to its association with cancer. However, the methodology used up to now has limited the scope of previous research. Our approach permits the identification of alleles in a fast and reliable way using their MVR codes, thus allowing association studies with cancer.