The Australian Competition and Consumer Commission ('ACCC') has been heavily criticised by business. This paper reports systematic, representative quantitative evidence on how large Australian businesses perceive the ACCC as a regulator in order to understand how these opinions are likely to affect compliance with trade practices regulation. First, we briefly review competing theories about what motivates businesses to comply or not comply with the law, and why their opinions of regulators matter for compliance. Second, we report survey results on business opinions of the ACCC along six dimensions that are explained in the paper - the ACCC's procedural and substantive justice, the likelihood and severity of ACCC enforcement action, the ACCC's strategic sophistication, how undogmatic it is, how accommodating it is, and whether it is biased in the way it targets large and small businesses for enforcement action. Third, we examine the extent to which our survey respondents' reported opinions of the ACCC are based on actual experience or not, and to what extent they are in line with their opinions of the other main national business regulators in Australia. Finally, we test the relationship between businesses' opinions of the ACCC and their attitudes towards trade practices compliance. We find that business opinions of the ACCC as reported in our survey are mostly not as negative as media reports might have suggested, and that opinions of the ACCC do relate to attitudes towards compliance, but not always in the ways that previous theory and research might suggest.