Observations and experiments on the pollination biology of Welwitschia mirabilis were carried out on six days between 6. and 14. February 1997, on a male and a female plant from the Welwitschia-plain in the Namib-Naukluftpark of Namibia. On the basis of the development of flowers, we can conclude, that the flowering period of Welwitschia lasts for about 8 weeks, from about mid January to about mid March. Only two flowers open every second day on the male cones. Due to its nectar production each male flower is attractive for insects for about four days but usually the pollen was harvested rightaway on the first or the second day by visiting insects. On most of the days, the production of micropylar drops of the male cones started at 11 a.m. and there is no resorption of the drops. If removed they regenerate in about an hour. About 20 female flowers of each cone produced a micropylar drop every day. Each female flower produces a new micropylar drop for about ten consecutive days in a diurnal rhythm. The production did not start before 12 a.m. and normally reached its peak at about 2 p.m. At 5 p.m. all drops were gone. They were either collected by the insects or reabsorbed by the plant. The beginning of the nectar drop production on the female plant was at least an hour later than that on the male plant. Keywords: Welwitschia mirabilis, Welwitschiaceae, Gnetopsida, pollination biology, Diptera, Hymenoptera - Flora of SW-Africa.