Con el objetivo de identificar la frecuencia de la caries dental en ninos y ninas menores de seis anos residentes en la ciudad de Medellin y describir los conocimientos y las practicas de cuidado bucal de sus madres, se realizo un examen clinico bucal a 365 ninos de los estratos socioeconomicos medio-alto (MA) y bajo (B) y se entrevistaron con base en una encuesta estructurada, 346 madres. El diagnostico de caries se baso en la propuesta de clasificacion de Pitts y Fyffe. La prevalencia de caries en el estrato MA fue del 48.4% y en el B del 58.3%. Se encontro caries dental desde el primer ano de edad, en ambos estratos. El promedio de superficies afectada por caries es de 3.4 y 6.6 para el estrato MA y B respectivamente. Se encontro una diferencia significativa en el nivel de escolaridad de las madres. El 42% de las madres del MA y el 50% del B afirman no haber recibido informacion sobre el cuidado bucal de sus hijos. En el momento del estudio se encontro que el 18% de los ninos presentaban habito prolongado del biberon y el 50% de las madres tenian la costumbre de dejar dormir al nino con el tetero. Los hallazgos de este estudio sugieren que la caries dental sigue siendo un problema frecuente en los menores de seis anos en Medellin; por lo tanto es indispensable asumir con continuidad la educacion de las madres y cuidadores para la verdadera promocion de la salud bucal, con tematicas especificas que trasciendan la accion educativa de la transmision de informacion a practicas de instruccion y adiestramiento para el desarrollo de destrezas. ABSTRACT The objective of this study was to identify the frequency of dental caries in boys and girls under the age of 6 in the city of Medellin, and to describe knowledge and oral health practices of their mothers. A complete oral examination was carried out on 365 children from Mid-high and low socio-economic status (SES), and 346 mothers were surveyed. Diagnosis of caries was based on Pitts and Fyffe‘s proposed classification. Prevalence of caries in the Mid-High SES group was 48.4% and in the lower SES it was 58.3%. Evidence of caries was evident since age one in both groups. The average number of surfaces with caries was 3.4 in the Mid-High SES and 6.6 in the low SES. A significant difference was found in the degree of education between mothers of both groups. 42% of mothers in the Mid-High SES group and 50% in the low SES group reported not ever having received information regarding oral healthcare of their children. At the time of the study, 18% of children presented a prolonged bottle habit and 50% of mothers indicated that they allowed their children to fall asleep with the bottle in their mouth. Findings of this study indicate that dental caries continues to be a frequent problem in children under the age of 6 in Medellin. It is therefore important to provide continuing education programs to mothers and caretakers in order to achieve a reliable oral health promotion with specific subjects which go beyond the traditional approach of transmitting information and focus on hands-on training programs which allow the development of abilities.