This study reports on functional morpheme (I, D, and C) production in the spontaneous speech of five pairs of children who have undergone hemispherectomy, matching each pair for etiology and age at symptom onset, surgery, and testing. Our results show that following left hemispherectomy (LH), children evidence a greater error rate in the use of functional category elements than their right hemispherectomy (RH) counterparts. Nevertheless, error rates are surprisingly low and comparable across groups. We interpret these results as (a) weak empirical evidence for a left hemisphere advantage in acquisition of functional structure, (b) strong support that functional structure is a property of all human grammars, and (c) strong support that each isolated developing hemisphere has the potential to acquire a grammar embodying and constrained by highly specific structural principles defining human language.