The linear growth and skeletal maturation of 19 boys with isolated gonadotropin deficiency, including four with anosmia (Kallmann's syndrome), are presented. With the exception of one prepubertal-age boy (less than or equal to 10 years) and five pubertal-age boys (greater than 10 years), all heights were within normal limits, but below the 50th percentile. With one exception, the bone age was retarded in all boys, even in prepuberty.