BM Monocerotis has a
rotation of the line of apsides with a period of 168 years, and an orbital
eccentricity of 0.18. The evidence for this rotation and eccentricity is (1)
the position of the secondary minimum (relative to the primary) has changed
0.062 period in phase over 23 years and; (2) the O-C curve (back to 1890) is
not straight, and appers to be part of a sinusoid. This paper also reports on
five minima timings, the light curve of BM Mon, and it spectrum.