The history and status of Balmer hydrogen-line photometry are briefly reviewed, and problems associated with calibrations in general are commented on.
The calibration work at Kitt Peak is described in some detail for B, A, and F type stars. The data used, the determination of intrinsic colours and colour excesses, photometric classification, and the relation of our indices to other people's are reviewed. With this background, the procedure used in establishing the absolute magnitude — Hβ calibration is given, and the preliminary calibration is presented. Finally, the work remaining to be done before the calibration is final is noted, and a comparison is given to Blaauw's zero-age main sequence calibration.