Hybridization and introgression in the European species of Euphrasia depend on the relationships between the species, on flower size and habitat. Hybridization between Euphrasia minima and Euphrasia salisburgensis was investigated in their natural habitat using artificial sympatric populations of both species in the Swiss Alps. The insect behavior in the populations suggests, that cross-pollination is likely to occur. A number of putative hybrids were detected by morphological characteristics, and their hybrid origin was verified using RAPD analysis. The predominance of RAPD bands in one of the species and the occurrence of these bands in some plants of the second species point to earlier introgression events. The number of hybrids found in the artificial populations together with results of earlier studies indicate that insect visits and cross-pollination in small-flowered Euphrasia species in lower alpine regions may be more common than has been suggested in the past.