Prior to the passage of the Crimes (Powers of Arrest) Act 1972 (Vic) which came into operation on 1 July 1972, there existed in Victoria not only the complex common law rules governing instances of arrest, but also a collection of more than 60 legislative provisions contained in more than 30 separate Acts. This paper sets out to examine some effects of this rationalizing Act. This report has an empirical base using records from a large and representative urban police station yielding, in this instance, 200 cases for analysis. It was found that the legislation had no discernible effect in changes of arrest versus summons rates for comparable offences, but a number of distinct features were isolated as being influential in determining the police decision to arrest or to handle matters by means of summons. These factors were found to co-exist prior to and after the implementation of the legislation, and did not appear to change as a result of the legislation. From this study it is concluded that there is an urgent need for some working guidelines to be set out in the relevant powers of arrest legislation. Such guidelines, absent in the present Act, confer on the police an unwarranted, and perhaps unwanted, degree of discretionary power. Proposals for reform are examined, stressing the need to develop an objective system whereby influential factors in the decision to arrest, leading to the suggestion that such systematic control both could and should be formalized by the legislature.