Sensory and motor developmental tests were designed to characterize spontaneous mutations in rodents. These tests are currently used to investigate developmental abnormalities associated with gene overexpression or gene targeting in mice. Here, we present an overview of our studies focused on 15 tests designed to measure sensory and motor development from birth to weaning in mice. Psychometric characteristics and factorial structure of these measures are considered first. The genetic correlates of these measures obtained with neurological mutants and gene mapping are compared. As a general rule, the contribution of genotype to the phenotypic variance of sensory and motor measures of development is low, inviting exploration of other sources of variation. Results from ovary transplantation, embryo transfer and fostering methods indicate that different components of maternal environment (cytoplasmic, uterine or postnatal) contribute to the behavioral phenotype. Although more difficult to detect, interactions between genotype and environment are involved.