The behaviour of orbital periods of early-type binaries is still
very little known; in some cases, perhaps shallow minima or long
periods make these variables not much attractive for observers.
Nevertheless, interesting results were obtained for this type
of binaries - e.g., in several cases, light-time effect due to a
third body, or variations of O-C values significantly
larger than measuring errors were found. Some of the present
authors have already discussed the subject (Mayer 1980, 1987;
Mayer et al. 1991, hereafter MWTN). In this note we give newly measured
times of minima for six variables and also discuss the periods in
cases where more data are available.
The stars selected are those with a longer observing history among
the OB eclipsing binaries; they are also included in our program to
determine absolute dimensions and evolutionary properties of such
systems. The only exception, AQ Cir, is a candidate to be included
in the program.