As far as the authors are aware, no standard technique has been described for the enumeration of infective trichostrongylid larvae recovered from faecal cultures. In experiments involving artificial infestations it is usually necessary to divide a concentrated suspension of larvae into a number of doses. In measuring the doses a dilution method may be used in which all the larvae in one or more aliquots taken from the diluted suspension are distributed on to a convenient number of slides and counted under the microscope. Alternatively, aliquots may be placed on the counting slide devised by Scott (1927). Such procedures are, however, time consuming and are fatiguing to the operator, where a large number of enumerations has to be made. They have the further disadvantage that the arbitrary dilution factor employed may result in too great a dispersion or conversely too great a concentration, either of which is undesirable from the point of view of accuracy and ease of counting.