Introduction: Sepsis represents a very important clinical problem in the ICU due to its high mortality and the dysfunctions caused on the skeletal muscles.Objectives: To evaluate the association between the rectus femoris cross-sectional area (RFCSA) and the muscular strength obtained at the bedside in patients forwarded to the intensive care unit (ICU) for severe sepsis and septic shock. Methods: A prospective cohort study. RFCSA was assessed by ultrasound on the following day of the ICU admission and monitored during hospitalization. The patients performed clinical tests of muscle strength (Medical Research Council (MRC) scale and handgrip dynamometry), when they could understand the verbal commands of the examiners. Results: In 37 patients hospitalized for sepsis there was a significant decline in RFCSA of 5.18 (4.49-5.96)cm2 on the 2nd day of ICU for 4.37 (3.71-5.02)cm2 at hospital discharge. Differently, the handgrip strength showed an increase from the awakening of 12.00 (7.00-20.00)Kgf to 19.00 (14.00-26.00)Kgf until hospital discharge. Patients in mechanical ventilation had a greater tendency to decline in the RFCSA compared to patients who did not receive mechanical ventilation, however without being significant (p=0.08). There was a negative association between RFCSA delta (2nd day of ICU – ICU discharge) and handgrip strength (r=0.51, p<0.05), and a male and SOFA score positive association with the RFCSA delta. Conclusion: There was an association of RFCSA with clinical muscle strength tests. In addition, it has been shown that sepsis can lead to short-term muscle degradation, regardless of whether they are submitted to mechanical ventilation or not.