expression patterns of parathyroid hormonerelated peptide pthrp and parathyroid hormone receptor type 1 pthr1 during human development are suggestive of roles specific for each gene that are not mediated through the pthrppthr1 paracrine signaling pathway close temporal and spatial relationships between pthrp and pthr1 gene expression are reported during fetal life in rats suggestive of a developmental role via a paracrine signaling pathway in agreement disruption of this signaling pathway is associated with developmental defects as documented in mice and humans surprisingly however only few organs are affected we report here pthrp and pthr1 gene expression during human embryofetal development we describe three patterns in some organs both genes are active handinglove fashion while in others either pthrp or pthr1 transcripts are detected in addition in some tissues expression of pthrp or pthr1 genes is transient abnormal development has been documented only for organs expressing both genes the patterns that we observe are compatible with specific roles for each gene not mediated through the pthrppthr1 signaling pathway