This book is about the study on comparative gross and micro anatomical details of the testis and epididymis of dogs and cats from pre and post-pubertal age groups. The gross morphological and morphometrical details of dogs and cats were discussed. The histological and histochemical observations were discussed in this books. The activity of the androgen receptors were studied in this book. The ultrastructure details of both cats and dogs were discussed based on the Scanning Electron Microscope study. This book will definitely be a goof refence for the researchers and students.