The relationship between blood pressure and pain sensitivity in a spontaneously hypertensive strain of rats (SH) was studied. Both analgesia and systolic blood pressure (SBP) were determined in SH and Wistar-Kyoto (WK) rats between 30 and 70 days of age. The SBP of the 30 day old SH rat was not significantly different from that of the WK rat (SH = 102±10 mm Hg; WK = 93±12 mm Hg). Howeverm, the yooung SH rat exhibited considerably more analgesia than corresponding, age matched, WK rats. The SH rat jump latency was 45±10 seconds whereas the WK rat latency was 21±6 seconds. Both naloxone and atropine attenuated the analgesia of the SH rat but did not significantly alter the response of the WK rat. Methyl-alropine did not affect either the SH or WK rat response. These data suggest the presence of higher endorphin-like activity in the SH rat and a possible relationship between endogenous opioid pathways and the development of hypertension.