The authors present a group of 67 patients, mean age 63 +/- 15 years, where they applied on account of suspected dysfunction of the sinoatrial node (SA) the atropine test (AT), 24-hour Holter monitoring and transoesophageal stimulation of the atria (TESP). The objective of the investigation was to test the reliability and yield of the mentioned methods and to investigate more closely the relations of their final indicators. Correlation analysis revealed a positive relationship between the maximal frequency during AT and the mean daily (r = 0.553, p < 0.001) and minimal frequency during Holter monitoring (r = 0.349, p < 0.0025). The recovery periods of the SA node were negatively related to the mean, minimal and maximal frequency during Holter monitoring. The relative rise of SF during the atropine test did not correlate with any Holter parameter nor with the recovery periods of the SA node. The length of the pause (Holter) did not correlate with any of the evaluated parameters. Based on the mentioned findings, the authors conclude that the diagnostic value of the mentioned non-invasive tests, when used separately, is limited but increases when the tests are combined.