An analysis of the effect of throttling on surge and rotating stall has been done to develop an insight on the possible behaviour of instabilities in a compression system subsequent to an initial disturbance. The ability to predict the nature of instabilities are highly important from the compressor design point of view since their consequences could result in widely varying difficulties with the fluid dynamic performance of the systems. The present paper discusses, in an approximate manner, the effect of throttle position in a compressor performance curve which is shown to create widely varying behaviour on fluid dynamic instabilities once the stall line is crossed. The physical reason for the behaviour is explained and the well-established Moore–Greitzer compression system model have been used for the present study. The results shown in this paper clearly elucidates the dominating effect of the operating parameter, the throttle, on the development of flow instabilities like rotating stall and surge. The trends of their behaviour reported in this paper are found to have a good agreement with the experimental results. As these results inform about the nature of instabilities that one could expect as the stall line is crossed, appropriate preventive measures could be adopted to avoid/control such instabilities.