The article evaluates the farmers' transaction costs defined as the weighted time spent on preparing their offer for two calls for tender for environmental services in agriculture which were carried out as a pilot project. Following a discussion of the specific need for research, the paper gives a brief introduction of the practical use of calls for tender and carries on to define the relevant transaction costs and introduce the methodological procedure. On the basis of three written interviews the time spent preparaing the offers and the individual monetary valuation of the time expended are discussed for both calls for tender. The results show the diverse individual transaction costs, their unequal relevance and also a decrease from the first to the second call for tender.