The effect of visits to nests of open-nesting passerines was investigated over two years using a randomized sampling design; the only such study ever undertaken in the UK. There was no overall effect of nest visiting on nesting success (the analysis had a power of 85% to detect a difference of 10% in success rates between control and visited nests). However, although thrushes and insectivores appeared to be beneficially affected by nest visiting, finches were detrimentally affected by nest visiting in one of the years. The effect of nest visiting did not differ between habitat, categorized into farmland, woodland and garden. The degree of exposure of the nest had no effect on nesting success but increases in the degree of disturbance made to a nest's surroundings paradoxically appeared to increase nesting success. A brief review of studies undertaken outside the UK also reveals little evidence for any effect of nest visiting on passerine nest success.