Trisomy 13 or Patau syndrome (PS) is a chromosomal disorder characterized by a well known presentation of multiple congenital anomalies. Our objective was to determine the clinical features and prognosis observed in a sample of patients with PS. The series was composed of patients with diagnosis of PS consecutively evaluated by a Clinical Genetics Service from a reference hospital of southern Brazil, in the period between 1975 and 2012. Statistical analysis was performed using PEPI program (version 4.0), with two-tailed Fisher's exact test for comparison of frequencies (P < 0.05). The sample consisted of 30 patients, 60% male, median age at first evaluation of 9 days. Full trisomy of chromosome 13 was the main cytogenetic alteration (73%). The major clinical findings included: cryptorchidism (78%), abnormal auricles (77%), congenital heart defects (76%), polydactyly (63%), microphthalmia (60%) and micrognathia (50%). Four patients (13%) simultaneously had micro/anophthalmia, oral clefts and polydactyly. Some findings were only observed in our sample and included, among others, preauricular tags (10%), duplication of the hallux (3%) and spots following the lines of Blaschko (3%). Mosaicism (20% of cases) had a statistically significant association only with absence of cryptorchidism. The median of survival was 26 days. Patients with and without mosaicism had similar median of survival. Our findings, in agreement with the literature, show that the anomalies in patients with PS can be quite variable, sometimes even atypical. There is no pathognomonic finding, which may make the early identification of these patients challenging. © 2013 Wiley Periodicals, Inc.