Neoadjuvant chemoradiotherapy for locally advanced rectal cancer has been shown to decrease rates of local recurrence and more than double the rate of sphincter-preserving surgery. There is now compelling evidence that pathological complete response is an independent predictor of likelihood of local recurrence, distal metastases, disease-free and overall survival in locally advanced rectal cancer following neoadjuvant chemoradiotherapy. Pathological regression grading can therefore guide clinical decisions about salvage surgical strategies, adjuvant therapy and long-term surveillance. No universally recognised regression grading system currently exists for pathologists presented with resected tumour specimens following neoadjuvant chemoradiotherapy. The purpose of this review is to highlight the relevance of accurate tumour regression grading in achieving optimal clinical care for patients with rectal cancer.