The report describes the principles of seismic refraction survey and typical site requirements followed by a general description of the types of equipment needed for a survey. Single-channel equipment is normally used with a hammer energy source. It is emphasised that preliminary interpretations and calculations should be made in the field to check that enough information has been collected for satisfactory analysis. Two types of analysis are described. The first assumes that refraction occurs at a plane interface and the depth below each shot point is calculated for a three layer case. The second technique can be used to calculate the depth of a refractor beneath a geophone, and formulae are given to extend this to three layers. For this extended analysis additional field data is needed. The final section of the report describes some of the unusual situations which may lead to inaccurate interpretation of survey data