Several methods, including the use of seralogy, are available for evaluating prey-predator relationships. Two basic methods involving precipitation and agglutination reactions have been utilised, both of which depend on the production of specific antisera with high titres. A critical account is presented of methods of preparing an'tisera, with particular reference to the amount of antigen required, the route of inoculation and testing antisera, together with a review of the five precipitation and two agglutination techniques available. The main limitations of A 1 7 2 p -F -L -BOREHAM and C. E. OHIAGU serological methods are the specificity of the arttisera and the difficulties in quantifying results unless assumptions are made as to the number of prey eaten at each feed. Details of studies employing serological techniques to identify the predators of specific prey and the food of invertebrates are given in two tables. The value of serological techniques is discussed in relation to the ecology of invertebrates by considering, as examples, the insect fauna on broom (Sarothamnus scoparius), predation of mosquitoes and the food of triclads. Errors in the quantification of predation may occur by including positive reactions resulting from carrion feeding or material ingested accidentally on plants by phytophagous arthropods.