Production data of 366 individuals in the Dohne Merino Development programme at the Dohne Agricultural Research Institute, were used for the estimation of the heritabilities of 15 production traits. Halfsib analyses were applied to data corrected for identifiable environmental factors and to uncorrected data. The magnitude of heritabilities for body mass increased from birth (0,208 t 0,142) to 180 days of age (0,528 ± 0,189). The value for 42 days of age( 0,017 ± 0,109) however, approached zero. The heritabitities for 12 and l8 month body mass (0,365 ± 0,166 and 0,341 ± 0,163) were also lower than that for 180 days of age. According to these results 180 day body mass appears to be the most promising selection criterion for lamb production with the Dohne Merino. Greasy fleece mass had a heritability of 0,292 ± 0,155 at l8 months of age. All the estimated heritabilities (excluding42 day body mass) fell within the ranges of highest and lowest values published for similar traits in other bleeds of sheep. Satisfactory genetic improvement may be expected therefore, when selecting Dohne Merino sheep for these characters on an individual basis.