As part of an assessment of stress during the training of guide dogs for the blind, blood pressures have been monitored in their main breeds. For this article a population of 227 Labradors, between 9 and 24 months of age, had indirect arterial blood pressures measured and means taken of five readings. They were ranked according to their pressures. Prior to the measurements, their character was independently assessed as "stress-prone" or "non-stress-prone" by their highly experienced and trained handlers. The pressure data distribution of stress-prone animals in the ranking was analysed; they were significantly more likely to be found at the high end of the blood pressure range for that population.