Some pacemakers are capable of storing in memory and then, upon command, reporting the frequency of pacing and sensing in either or both cardiac chambers as well as other features of pacetnaker function. Rate and possibly sensor histograms can be generated automatically by the system to facilitate an assessment of its behavior over a period of time. Although available in some single‐ chamber Vitatron pacemakers and the Siemens‐Pacesetter Sensolog, this paper reviews the utility of this technology in both single‐ and dual‐chamber Intermedics units in the assessment of programmed rate and AV interval parameters and overall pacing system function. In the Intermedics' systems, this capability is called Diagnost