Abstract The commonest means of laboratory evaluation/screening of scale inhibitors for oilfield applications is by conducting scale inhibition jar tests. This paper focuses on several aspects concerning barium sulphate scale inhibition jar tests and highlights three particular factors which may influence the test outcome and the ranking of an inhibitor's performance as compared with others. The work presented in the paper confirms the critical importance of temperature. It proves that filtration of a supernatant sample when taken from the test jar for Ba analysis could lead to erroneous results on barium sulphate inhibition efficiency. This investigation also indicates that chelating agents may reduce inhibitor inhibition efficiency against barium sulphate. However, such an effect is found to be far less significant than that reported elsewhere.