Thirty Karakul ram lambs, ten each born in summer, winter or spring were raised from birth to an age of 240 days with pen feeding to study the influence of season of birth on puberty and testis growth. During this period the average body mass and testis circumference increased linearly and were correlated (r = 0,97) highly significantly (P<0,001). A regression equation Y = 0,5568 + 0,3277X (n = 102; Sy.x = 0,9291) where Y = testis circumference (cm) and X = body mass (kg) was calculated to predict testis circumference from body mass. From an average age of 80 – 152 days the average testis circumference increased more rapidly than the average body mass. Season of birth did not significantly influence the average body mass and testis circumference at anatomical and physiological puberty. Anatomical and physiological puberty occurred respectively at a mean age of 123,8 ± 21,7 and 139,6 ± 15,4 days, body mass of 31,2 ± 3,3; 33,2 ± 4,0 kg and testis circumference of 11,0 ± 1,5 and 12,4 ± 1,1 cm (n = 26 and 30; ± SD) during the rapid testiscular growth phase.