Monthly report for March 2000 by Christian A. Hummel: Hummel attended the NPOI quarterly meeting in Flagstaff, and then helped the two following days to clean feed pipes. Hummel finished a first draft of a paper on Zeta Orionis and sent it to the co-authors for comments. Hummel prepared the poster for the IAU 200 Symposium in Potsdam. He also presented this poster at the Washington Area Astronomers Meeting. Hummel gave a talk at the SPIE conference on Interferometry in Optical Astronomy, in Munich.