The aim of this study was to evaluate the effect of cleaning methods, artificial aging and of saliva contamination of four light-curing (Ultraseal XT®plus, Conseal f, Diaseal, Smartseal®opaque) and one self-curing fissure sealants (Delton®FS+opak). 400 molars were included. Following prophylaxis with Prophyflex®, one half of the teeth saliva was placed. The fissure sealants were applied as recommended by the manufacturer. One half of the teeth was thermocycled (5-55 degree celsius, 5000 cycles). Following that, all teeth were immersed in methylene blue for 48 hours, rinsed, sectioned and examined with digital light microscopy. Significantly higher average microleakage scores were obtained after thermocycling and saliva contamination (p < 0.05; Tukey`s test). In particular, Delton yielded the lowest microleakage scores after artificial aging (p < 0.05;Tukey's test). Within the limitations of the present study, it can be concluded that artificial aging and saliva contamination increased microleakage of the five fissure sealants significantly.