Introduction: Early neonatal screening detects several congenital diseases, which can be diagnosed and treated sooner to decrease the morbi-mortality of children. Objectives: To detect abnormal values of TSH and PKU and recognize early cases of hipotyroidism and phenylketonuria. Design: Prospective and descriptive study. Place: Centro Médico Especializado" CEMES". La Paz. Bolivia. Methods: From 1997 to 2010 we determined the levels of TSH and PKU in all healthy newborns in CEMES through blood spots in filter paper. We excluded premature and sick babies. The study was performed after the second day of life. The abnormal TSH levels were immediately checked by serological testing. The number of newborns was 2.142 and 224 were excluded for different reasons. The final number was 1.918 patients. Results: We found 31 positive TSH cases but confirmed only one newborn with congenital hypothyroidism, which turned out to be transient and all PKU testing was negative. Conclusions: We found one case of hipothyroidism in 1.918 patients and no cases of phenylketonuria in 808 patients. The neonatal screening is easy to perform, cheap and should be performed in all newborns.