Globally, power lines cause significant mortalities of birds through collisions and electrocutions, yet this problem has received only sporadic attention in Namibia. Vehicle-based surveys were undertaken every three months for one year to record mortalities of large birds along 349 km of transmission power lines in the Succulent and Nama Karoo biomes of southern Namibia. Four different line designs and transmission capacities were sampled: 66, 132, 220 and 400 kV. The clearing survey collected 80 carcasses; thereafter 197 bird mortalities were recorded over 12 months, of which 89% were identified to be collisions. Thirteen large bird species were recorded dying from collisions, with Ludwig’s Neotis ludwigii and Kori Bustards Ardeotis kori comprising 81% of all fatalities. There was a significant seasonal difference in collision rates, but no significant sex bias among bustard mortalities. Collision rates tended to be greater (but without statistical significance) on higher capacity lines, although the 66 kV line was the only line sampled in the Succulent Karoo, so was not directly comparable with higher capacity lines in the Nama Karoo. Collision mortalities along the four capacities of transmission lines averaged 0.5 birds km-1 year-1, similar to rates reported in the Karoo region of South Africa. These results confirm the very serious threat of this hazard to Ludwig's Bustard in particular. Suggestions for mitigation on new power lines are given, but the problem of thousands of kilometres of existing transmission power lines remains unresolved. Keywords: bustards, electricity grid, mitigation measures, mortality rate, power line survey.