This treatise will focus on the review of labour arbitration awards provided for under the oversight of the Commission for Conciliation, Mediation and Arbitration (CCMA), bargaining councils, statutory councils, accredited private agencies and approved private arbitration tribunals. The general grounds of review applicable to the arbitration awards of the different bodies are set out. Thereafter the case of Carephone (Pty) Limited v Marcus NO & others (1998) 19 ILJ 1452 (LAC) is analysed and the core principles pertaining to the justifiability test are clarified for the first time in the forum of the Labour Appeal Court. The judicial rationale for the relevance and applicability of the test to CCMA arbitration proceedings and criticisms of the test are examined. The justifiability tests are only applicable to review proceedings in CCMA matters and not available to private arbitration review matters. There are however three approaches which are being suggested for the application of the justifiability tests to private arbitration review. Firstly, it is suggested that the Arbitration Act could be interpreted to include the justifiability test under the statutory review grounds. Secondly, the arbitration agreements could be interpreted to include an implied term that the arbitrator is under a duty to give justifiable awards. Finally, it can be submitted that the law should be developed by reading into all arbitration agreements the ability to arbitrators to give justifiable awards. Since the judgment of Sidumo v Rustenburg Platinum Mines [2007] 12 BLLR 1097 (CC) various critical questions arose in relation to the interpretation and application for the purpose of dealing with subsequent review applications. Firstly, this research paper will seek to establish whether the courts in subsequent matters to the Sidumo judgment have interpreted reasonableness as a test or ground for review. Secondly the research paper will scrutinise case law whether the reviewing court is entitled to rely on and consider reasons other than those provided for by the commissioner in his award to determine inter alia, the reasonableness of his decision arrived at. The Constitutional Court in the Sidumo case rejected the so-called employer’s test, stating that ultimately the commissioner’s sense of fairness is what must prevail and not the employer’s view. Consequently an impartial determination whether or not a dismissal was fair is likely to promote labour peace amongst the labour force. The test arrived at by the Constitutional Court in the Sidumo case for determining whether a decision or arbitration award of a CCMA commissioner is reasonable, is a stringent test that will ensure that such awards are not easily interfered with. The question to be asked in determining whether there has been compliance with the standard is whether the decision of the commissioner is one which a reasonable decision maker could have reached. This approach will underpin the primary objectives of the Labour Relations Act which is the effective resolution of disputes. This finding will be apparent from important cases decided and discussed after the Sidumo landmark ruling.