Introduction: The most frequent complication after total thyroidectomy is hypocalcemia. It is difficult to predict it. The objective of this paper is determinate if measurement of parathormone 6 hours after total thyroidectomy can predict symptomatic hypocalcemia, and determinate associated factors in the development of this complication. Material and Method: Prospective case series. Patients that underwent total thyroidectomy between 2006 and 2008 in our Hospital. We registered epidemiological data, related surgery factors and measurement of parathormone 6 hours after surgery. Hypocalcemia symptoms were registered. We used statistical analysis considering significant p < 0.05. Results: We included 82 patients. Median age was 53.2 years. 79.3% were female. The average of parathormone 6 hours after surgery was 28.7 pg/dL. Sensibility was 100%, specificity 79.4%, positive predictive value 59.4%, negative predictive value 100% and accuracy 84.1% to predict symptomatic hypocalcaemia. A statistical association among levels under the normal base line of parathormone and symptomatic hypocalcemia was detected (p < 0.0001). Relative risk was 4.84. Univariated analysis showed association between hypocalcemia and pre-operative thyroid cancer diagnosis (p = 0.01), cervical dissection (p = 0.03) and level of parathormone (p = 0.002). Multivariated analysis showed that only the level of parathormone associates with hypocalcemia (p = 0.002). conclusion: The measurement of parathormone allows identifying which patients are at risk of presenting symptomatic hypocalcemia after total thyroidectomy.