Studies in mice and rats support the hypothesis that ventilation and its components (frequency and tidal volume) are determined to a significant extent by genetic mechanisms. The question can no longer be 'is there a genetic effect?' but rather 'how strong is the genetic component?' and 'what genes are involved?' The computational analyses of selectively bred animals now offer powerful tools to begin to dissect the genetic factors that track with ventilatory traits. Control of the conditions in the colony and in the laboratory are keys to reducing the environmental 'noise' and increasing the likelihood of detecting gene loci that correlate quantitatively with phenotype values before and during the response to chemosensory challenges. Knowing the chromosomal location of genes for ventilation will then permit the identification of proteins systems responsible for the structural and functional components for respiration.