SUMMARY: In conjunction with comparative studies of Xylocaine® and a new local anaesthetic agent, L67, it could be demonstrated that a greater and more statistically reliable difference in duration in favour of L67 could be obtained with finger blocks than with the customary cutaneous wheals. A correlation between age and duration of anaesthesia was obtained for finger blocks with both agents. The effects of concentration and age upon duration and latent period were more closely studied for L67. Age was found to affect duration but not the length of the latent period. Concentration affected duration in the older age groups but not in the younger. The length of the latent period was inversely proportional to concentration in all age groups. The results stress the importance of uniformity with regard to age between the groups when different groups are compared in clinical trials of local anaesthetics. Furthermore, a practical consequence is that greater attention should be paid to the concentration of the local anaesthetic used for finger blocks in older persons.The effect of age is supposed to depend upon variations in the vascularization of the anaesthetized region. If this is the case, it remains to be determined whether the differences in the duration of anaesthesia for different agents without vasoconstrictors depend upon differences in the effects of the agents upon blood vessels more than upon different affinities for nerve tissue.