SUMMARY Background: Mental retardation is one of the most frequent major handicap, with a 1-3 % frequency in the general population, it appear a major problem of public health. The recent progress of molecular biology and cytogenetic allowed to identify new genes for non syndromic autosomal recessive mental retardation (NSAR-MR). Aim: Genetic analysis of NSAR-MR: the GRIK2 gene (6q16.3-q21) and the TUSC3 gene (8p22). Methods: Four Tunisian families with NSAR-MR were included in this study. Genotyping was made using polymorphic microsatellite markers and statistical analysis was validated using the Fast Link programme of the Easy linkage software (V4:00beta). Results: Genotyping and linkage analysis excluded linkage of the GRIK2 gene and TUSC3 gene. Conclusion: Our results confirm the extreme genetic heterogeneity of NSAR-MR.