BACKGROUND: Guidelines from medical societies suggest recommendations for the appropriate request of tests. In 2009, the Brazilian Society of Cardiology (BSC) published new guidelines for transthoracic echocardiography (TTE) request. OBJECTIVE: To evaluate the prevalence of Class III requests for TTE, as defined by the BSC Guidelines and analyze these requests profile comparing a public university hospital (PUH) with a private cardiology hospital (PCH). METHODS: We prospectively evaluated 779 consecutive outpatient TTE requests: 391 from the PCH and 388 from the PUH between December 2009 and May 2010. The indications studied were classified accordingly to the BSC guidelines. Request distribution was compared by Chi-square test. Statistical significance was set at p < 0.05. RESULTS: Of the 779 requests, 61 (7.8%) were considered Class III. Of these 14 were from the public and 47 from the private hospital. The distribution of requests was statistically different between institutions (p < 0.001). Check-up in asymptomatic patients was the main inadequate indication, with 37 cases (33 in the private institution- 89.18%), followed by evaluation after angioplasty in 9 cases (8 in the private institution - 88.88%); ventricular function monitoring in patients with stable heart failure in 6 cases (4 in the public institution - 66.66%), post-bypass surgery in 5 cases (4 in the private institution- 80%), and evaluation of nonspecific electrocardiographic abnormalities in 4 cases (4 in the public institution - 100%). CONCLUSION: Asymptomatic patients' assessment was the main cause of inadequate TTE requests, which differs between institutions: routine check-up in the private and heart failure in the public hospital.