The entomogamic Pulsatilla vulgaris, which flowers early in the year, exhibits special adaptations to safeguard against self-pollination. In order to characterize its pollination strategy a population was studied for 4 years in the Kaiserstuhl (southwestern F.R.G.). During the vegetation period individually marked flowers were observed daily. Besides flower morphology the analysis includes opening and closing of the perigon during the anthesis, anther dehiscence and pollen release, receptivity of the stigma, the number of pollen grains per anther and the germination of pollen grains. The studied features are discussed in the light of their importance for their flowers visitors and for pollination. The insect species, the number of their visits per flower, their behaviour as well as the time of pollination and the amount of fruit set were analysed. The existing temperature conditions influenced several processes in the different flower parts. A temperature of at least 12 °C is important since it marks the onset of flower budding, invokes the opening and closing of perigon, and influences the dehiscence of anthers. Also at 12 °C the activity of flower visitors, mainly bees (Andrenidae, Halictidae ) starts. Flowers appearing early in the flowering time of the population live longer than those appearing later, therefore the portion of synchronic flowers increases in the course of the population development. The resulting consequences are discussed with regard to population biology. The flower shape, the opening and closing of the perigon and the accessibility of different flower parts to flower visitors altogether increase the probability that insects touch the stigma and transfer pollen grains, and they all are determined by the involucrum. The influence of the involucrum decreases with increasing growth of the pedicel. Anthers located in the upper part of the androeceum bear a higher number of pollen grains than those in the lower part. The dehiscence of the anthers in the androeceum is staggered, the importance of this adaptation for the flower, the population and the flower visitors are discussed. A total of 37 species of Hymenoptera Apoidea visited the flowers of P. vulgaris, but only 2 species serve as pollinators in the study area (2 localities) in the Kaiserstuhl: Lasioglossum lineare (Schck.) (Halictidae) and with less importance, Andrena bicolor F. (Andrenidae). The remaining flower visitors of Hymenoptera Apoidea amount only to 21 % of the total. A high portion of these species exists only in those years when the climatic conditions cause a late flowering of P. vulgaris. Diptera, Coleoptera, Lepidoptera and Hymenoptera (non -Apoidea ) do not contribute significantly to the pollination of P. vulgaris in the study area. This conclusion is based on 1,138 observed flower visits. The behaviour of Lasioglossum lineare and Andrena bicolor (i.e. approach to the flower, landing, pollen gathering, intake of nectar, daytime preference for flower visiting) are analysed. The total number of flower visitors per flower, the time of pollination, the amount of fruit set and several other parameters could be correlated. The results indicate that the fruit set of the studied population in the Kaiserstuhl exceeds 70 %, although only a few hours of favourable weather conditions actually exist during the flowering time of the population in average years. The amount of fruit set is not correlated with the time of flowering within the population. The main pollinator in the study area of Kaiserstuhl is Lasioglossum lineare. This social species demonstrates many adaptations which ensure the pollination of P. vulgaris. One important factor is its predominantly subcontinental distribution. L. lineare and P. vulgaris s.I. belong to the same geoelement. In Westhalten (Alsace) the main pollinator other than Apis mellifera L. is Lasioglossum malachurum (K.). Lasioglossum lineare and Andrena bicolor do not reach a sufficient number of individuals at this site. These differences are discussed in the light of areageographical and historical aspects. L. malachurum has a submediterranean/subcontinental distribution.