Electrocardiographic studies made on conventional pigs by different authors (Bartels,1972; Rubio,1987;Fernández,1997) have indicated that the duration of the parameters underwent modifications with physical maturation. ECGs were performed on 25 minipigs (coming from the line selected by the University of Navarre) belonging to the Animal Experimentation Service of the University of Córdoba, at the age of 5, 20, 45 and 90 days, with the aim of checking the possible differences in the ventricular electric processes like, the consequences of age. The results show a diminution in their heart rate as their age increased, with the 5-day-old piglets showing the maximum values (231.04 beats/min) and the 90-day-old pigs the minimum value (125.99 beats/min). The decrease observed was correlated with an increase in the duration of all the parameters analyzed. The minimum value of the cardiac cycle duration corresponded to the 5-day-old (0.260±0.066 sg) with a increase (0.406sg.; 0.444sg.; 0.466sg.) for the different ages, respectively. A t–Student test revealed differences (99.9%) when comparing the youngest pigs (5 days) with the rest. The mean value of the ventricular depolarization increased with the age, showing values of 0.027sg(5 days),0.031sg.(20 days),0.032sg.(45 days) and 0.036sg.(90 days); a similar evolution took place in the heart size. The mean values for the Diastole/Systole increased as the animal grew (0.802; 1.094; 1.111 y 1.143), which was indicative of a better cardiac recovery. It was concluded that the electrocardiographic register in minipigs was affected by their physical maturation, with a very high significance level as from 5 days of age.