The experimental animals were 60 days old rats which had been suffering from undernutrition during day 1 till day 20 of their early postnatal life. The recovery from the retardation in brain development induced by the experiment was investigated by quantitative light microscopical methods in GOLGI impregnated material. In pyramidal neurons of lamina III or V of the anterior cingulate cortex several neuronal parameters were estimated in a single dendritic field (EDF) indicative for the development of the dendritic tree and spine distribution of these neurons. The results demonstrate a sufficient recovery in those cases when the rehabilitation is beginning already within the period of intensive brain growth. The duration of this growth spurt is prolongated in the experimental animals. Therefore, after the starvation period the brain is supposed to have some potency for further neuronal differentiation, also beyond the 20th day of life. This fact is considered to be decisive for a full recovery. After the starvation period at day 20 the lamina V pyramidal neurons were found to have developed a significantly smaller dendritic tree (minus 15%) equipped with a strongly reduced spine number (minus 30%). After the recovery time of 40 days the control values were reached, moreover, the spine density in apical dendrites was enhanced in comparison to controls. Likewise, in the lamina III pyramidal neurons of experimental animals, the apical dendritic tree was shortened by 25-30%, the basal dendritic tree by 10% at the end of the undernutrition period. However, after recovery of 40 days the dendritic tree of these neurons developed a significant overshoot of 15-20% in comparison to controls. The spine number at basal dendrites was similar to controls, but at apical dendrites significantly higher. The differences in the recovery pattern of both neuron types are explained by the hypothesis that the lamina III pyramidal neurons are phylogenetically younger and, therefore, have a considerably longer postnatal differentiation phase. Thus, they show a stronger retardation in growth by the undernutrition. However, during rehabilitation and recovery they show a larger increment in growth and differentiation.