Growth hormone (GH) replacement unequivocally benefits growth, body composition, cardiovascular risk factors and quality of life. Less is known about the effects of GH on learning and memory. The recent paper on 'early onset - GH deficiency (GHD) results in spatial memory impairment in mid life - and is prevented by GH supplementation' by Nieves-Martinez importantly adds to this literature. Other data suggest that GH beneficially affects cognitive function in rats. In man, treatment of GHD has been associated with improvements in measures of memory and attention. There are also differences in verbal memory of patients with childhood onset GHD. Further questions remain, and the beneficial effects or otherwise of treating GHD in different age groups remain to be better defined. Certainly for reasons of maturation of neural connections and their development to young adulthood contemporaneous with rises in GH and IGF1 make these important areas for further study in man. Lastly because of what we already know in terms of cognitive effects of GHD, it is important to replace GH when studying other potential causes of adverse effects on cognition, for example, with radiotherapy.