This review summarises evidence of the effectiveness of handwashing and the use of soap as a public health intervention against Ascaris infection, in terms of both prevalence and intensity. Literature in five major languages was searched and data were retrieved from 15 papers. The evidence of the effect of handwashing in general upon both prevalence and intensity of Ascaris infection is inconclusive. However, the use of soap in handwashing is protective against Ascaris infection with respect to prevalence. There is no direct evidence that it reduces the intensity of infection.