This report contains an analysis of data on wave transmission. It is restricted to wave transmission at low-crested permeable breakwaters. All data used are from tests with irregular waves. These data were earlier gatherd in Delft Hydraulics' report: "Data on wave transmission due to overtopping by J.W. van der Meer ((1990). Aim of the research: Until now wave transmission is described by various formulas in which terms appear which contain more than one parameter. This makes it hard to recognize the influence of an individual parameter. The aim of the analysis presented in this report is to look at all parameters involved in a separate way and to come up with a formula which can predict wave transmission at low-crested breakwaters. This formula should be practically usable and reasonable reliable.