A survey conducted among hospital laboratories has yielded data from 640 institutions concerning the use of diagnostic kits and reagents in Canada. 2. Kits designed to test for chemical constituents were most frequently used in hospitals of 51 to 600 bed capacity whereas the ones for enzymes were most extensively used in 201 to 700 bed-size institutions. Kits based on the CPB principles were generally used in hospitals of more than 200 beds whereas those based on RIA were only in frequent use where the bed capacity was 351 or more. 3. The following tests were most often performed by kits: aminotransferases, amylase, urea, LDH, phosphatases, glucose, CPK, bilirubin, calcium, uric acid, T-4, T-3, digoxin and vitamin B12. 4. The survey reflects a continuing and increasing usage of in vitro diagnostic kits and associated blood analyzer systems. It also indicates a significant adoption of assay kits which utilize RIA and CPB principles.