Audit is one of the most important activities during controlling and verifying the objectivity, the reality, th accuracy and the legality of the company's entire business, which, of course, includes financial operations. Therefore, the audit endeavors to detect errors occurring during the business process and to remedy them ina n extremely short time. The audit is carried out by auditors who compile their reports, where they have to be guided by different principles and standards, and they also have an independence in their opinions. There are different types of audit, but within the graduate thesis we will focus on the state audit, more specifically on the environmental audit, that is one of the kinds of state auditing. State audit involves controlling and reviewing the state budget as well as the budgets of local and regional units and financial statements of state or public companies. An environmental audit as one of the sub-types of state audit concerns the control of state, local and regional revenues and environmental expenditures. Within the scope of the graduate thesis, the revenues and expenditures will be analyzed, as well as the environmnetal investments of the Republic of Croatia, and will explain the theoretical aspect of the audit, audit process, state audit and environment, environmental protection and environmental audit.