In the practice of radiotherapy, various concepts like NSD, CRE, TDF, and BIR are being used to evaluate the biological effectiveness of the treatment schedules on the normal tissues. This has been accepted as the tolerance of the normal tissue is the limiting factor in the treatment of cancers. At present when various schedules are tried, attention is therefore paid to the biological damage of the normal tissues only and it is expected that the damage to the cancerous tissues would be extensive enough to control the cancer. Attempt is made in the present work to evaluate the concent of tumor significant dose (TSD) which will represent the damage to the cancerous tissue. Strandquist in the analysis of a large number of cases of squamous cell carcinoma found that for the 5 fraction/week treatment, the total dose required to bring about the same damage for the cancerous tissue is proportional toT−0.22, whereTis the overall time over which the dose is delivered. Using this finding the TSD was defined asD⋅N−p⋅T−q, whereDis the total dose,Nthe number of fractions,Tthe overall timepandqare the exponents to be suitably chosen. The values ofpand q are adjusted such thatp+q≤0.24, andpvaries from 0.0 to 0.24 andqvaries from 0.0 to 0.22. Cases of cancer of cervix uteri treated between 1978 and 1980 in the V. N. Cancer Centre, Kuppuswamy Naidu Memorial Hospital, Coimbatore, India were analyzed on the basis of these formulations. These data, coupled with the clinical experience, were used for choice of a formula for the TSD. Further, the dose schedules used in the British Institute of Radiology fractionation studies were also used to propose that the tumor significant dose is represented byD⋅N−0.18⋅T−0.06.