We report a comparative study of the growth hormone nycthemeral secretion and the response of growth hormone secretion to pharmacological stimulation tests in 38 children with growth retardation. Two groups were separated according to the results of the nycthemeral growth hormone secretion study: a group of 26 children with normal secretion (mean maximum peak: 26.6 +/- 9.6 ng/ml and mean integrated concentration: 4.26 +/- 2.13 ng/ml/min) and a 2nd group of 12 children with hyposecretion (mean maximum peak: 6.7 +/- 2.6 ng/ml and mean integrated concentration: 1.08 +/- 0.45 ng/ml/min). There was no correlation between nycthemeral secretion and the responses to pharmacological tests. Thus, in the group with hyposecretion, 5 children had normal responses to a pharmacological test and in the group with normal secretion 13 children had intermediate responses to 2 pharmacological tests and 4 had dissociated responses. Thus, it appears mandatory to perform 2 different pharmacological tests in any investigation and to study the nycthemeral secretion in cases with intermediate or dissociated responses as well as in cases with normal responses when the clinical picture is consistent with growth hormone deficiency.