Blood pressure is usually determined by arm sphygmomanometry. However, this technique does not allow continuous blood pressure monitoring. Over the last years, a technique introduced by Peñaz makes it feasible to determine blood pressure noninvasively and continuously from the finger artery. Study on 46 normotensives showed that both methods have high retest-reliabilities for systolic blood pressure while for diastolic blood pressure, arm sphygmomanometry resulted in lower reliabilities than the Peñaz-method. Between-method-comparisons showed only small correlations. Diastolic blood pressure levels were significantly lower in the Peñaz-method than in arm sphygmomanometry. In conclusion, blood pressure levels determined by arm sphygmomanometry and the Peñaz-method differ systematically because of different methodologies. If blood pressure or blood pressure changes are determined, the method and the circumstances of its application need to be carefully reported.