The purpose of this study was to assess the effect of low dose hPTH(1-34) on bone mass and structural connectivity of the lumbar vertebrae in normal adult beagles. Sixteen 19-20 month-old beagle dogs were randomized into 4 groups. The vehicle control group was injected saline daily, the sequential group was injected 0.375 μg/kg of hPTH(1-34) daily for 4 weeks, then off 8 weeks, and this was once repeated. One time group was injected the same dose of PTH once per week, and three times group was given it three times per week subcutaneously injected for 24 weeks. Calcein double labeling was performed at the end of the administration. Seven μm thick undecalcified sections of 5th lumbar vertebral body were assessed by bone histomorphometry and two-dimensional nodestrut analysis. In three times group, OS/BS, OV/BV, MAR showed a significant increase compared to vehicle control group. No significant changes were observed in BV/TV, MS/BS, BFR/BS among 4 groups, however there were significant differences in N/Tm/TV, Nd.Tm/TV, and Cr.Nd/TV between vehicle control and three times group. These results suggested that an increase of bone formation and a tendency of improvement of trabecular connectivity by intermittent low dose PTH administration in the lumbar vertebrae of adult dog.