The detection of anti-tumour cell-mediated immunity in cancer patients by the leucocyte adherence inhibition test was reported in 1974. The test has since been variously described as capricious, non-reproducible and invalid. These criticisms may be related to the critical and difficult to reproduce washing procedure of the original test. In order to overcome this, an automated assay has been developed. The apparatus devised allows replicate samples to be tested concurrently. It consists of 30 X 100 microliter syringes whose barrels have been extended by nylon cones (1500 microliter) and whose plungers move synchronously. Suspensions of washed peripheral blood leucocytes with serum and tumour antigen are incubated in the syringes. Non-adherent cells are washed from the syringes by fully withdrawing their plungers and allowing entry of 1,000 microliter of saline from the cones. The effluent containing non-adherent cells is collected and automatically counted. A one-way analysis of variance using a statistical package for the social sciences (SPSS) programme for the syringe, wash and drainage volumes indicates that the variance between syringes is so small that sub-division of the syringes into control and test groups is justified. The crudity of the prototype, however, results in variations between volumes aspirated on successive occasions. Preliminary clinical studies show that 13/15 patients have a test result which correlates with their Mantoux status.