To determine the effect of adding dexmedetomidine to bupivacaine for neuraxial anesthesia. Sixty-six patients were studied between April and May 2008 in the University of Jordan, Amman Jordan. They were randomly assigned into 3 groups, each receiving spinal bupivacaine 12.5mg combined with normal saline (group N) Dexmedetomidine 5 microg (group D5), or dexmedetomidine 10 microg (group D10). The onset times to reach T10 sensory and Bromage 3 motor block, and the regression times to reach S1 sensory level and Bromage 0 motor scale, were recorded. The mean time of sensory block to reach the T10 dermatome was 4.7 +/- 2.0 minutes in D10 group, 6.3 +/- 2.7 minutes in D5, and 9.5 +/- 3.0 minutes in group N. The mean time to reach Bromage 3 scale was 10.4 +/- 3.4 minutes in group D10, 13.0+/-3.4 minutes in D5, and 18.0 +/- 3.3 minutes in group N. The regression time to reach S1 dermatome was 338.9 +/- 44.8 minutes in group D10, 277.1 +/- 23.2 minutes in D5, and 165.5 +/- 32.9 minutes in group N. The regression to Bromage 0 was 302.9 +/- 36.7 minutes in D10, 246.4 +/- 25.7 minutes in D5, and 140.1 +/- 32.3 minutes in group N. Onset and regression of sensory and motor block were highly significant (N vesus D5, N versus D10, and D5 versus D10, p<0.001). Dexmedetomidine has a dose dependant effect on the onset and regression of sensory and motor block when used as an adjuvant to bupivacaine in spinal anesthesia.