['To present the clinical, genetic, biochemical, and molecular findings in two Chinese siblings with X-linked recessive Kallmann syndrome (KS).', 'Case report.', 'University medical center.', 'Two Chinese siblings.', 'Clinical evaluation, hormone assays, and gene mutation research.', 'Endocrinologic evaluation and genetic analysis.', 'A missense mutation of KAL1, c.1828G>A, led to pVal610Ile substitution in two brothers with KS; their mother is heterozygous for this missense mutation encoded by single-nucleotide polymorphism rs2229013.'] Is the KAL1 pVal610Ile mutation a recessive mutation causing Kallmann syndrome?