This experiment was designed to assess transcript abundance variation in mice under normal lab conditions. Four tissues were sampled from twelve 10-week old male C57BL/6J mice. Six pairs of siblings were co-housed from weaning under uniform environmental conditions. From each mouse duplicate samples were obtained of adipose (inguinal fat pad), heart, kidney, and liver tissues by splitting whole organs or tissues prior to homogenization and RNA extraction. Adipose, heart, and liver tissues were coarsely cut into pieces and divided into two samples that were homogenized separately prior to RNA extraction. The left and right kidneys were processed separately. This sampling design allows the variance for each gene to be partitioned into within-mouse and between-mouse components with a division line that corresponds to the partitioning of the tissues.