The primary objective of this study was to evaluate the applicability of World Health Organization (WHO), Southwest Oncology Group (SWOG) and Response Evaluation Criteria in Solid Tumours (RECIST) guidelines when evaluating the response of cytotoxic agents in solid tumours. Patients with a solid tumour who were planned for standard chemotherapy, were aged more than 18 years and had an anticipated life expectancy of at least 12 weeks were included in the study. Patients received chemotherapy using standard protocols and were required to have a pre-treatment evaluation of tumour burden on CT. Subsequent response assessment was performed every two cycles. Each patient was evaluated by all three criteria (WHO, SWOG and RECIST) to check the applicability of a specific criterion during routine clinical practice. In total, 80 patients were included in the study. Out of these, the response criteria displayed discordance in 17 (21%) patients. Of these 17 patients, RECIST criteria were not applicable for 6 patients owing to the small lesion size. The present study shows that a particular guideline may be useful in establishing uniformity of evaluation in a desired study population but may not be the best for that population during routine clinical practice. It also indicates that each of the guidelines has its own applicability and that no guideline can outweigh the other during routine clinical practice.