  We present the results of a near-infrared monitoring programme of a selected
sample of stars, initially suspected to be Mira variables and OH/IR stars,
covering more than a decade of observations. The objects monitored cover the
typical range of IRAS colours shown by O-rich stars on the Asymptotic Giant
Branch and show a surprisingly large diversity of variability properties. 16
objects are confirmed as large-amplitude variables. Periods between 360 and
1800 days and typical amplitudes from 1 to 2 magnitudes could be determined for
nine of them. In three light curves we find a systematic decrease of the mean
brightness, two light curves show pronounced asymmetry. One source, IRAS
07222-2005, shows infrared colours typical of Mira variables but pulsates with
a much longer period (approx. 1200 days) than a normal Mira. Two objects are
ither close to (IRAS 03293+6010) or probably in (IRAS 18299-1705) the post-AGB
phase. In IRAS 16029-3041 we found a systematic increase of the H-K colour of
approximately 1 magnitude, which we interpret as evidence of a recent episode
of enhanced mass loss. IRAS 18576+0341, a heavily obscured Luminous Blue
Variable was also monitored. The star showed a continued decrease of brightness
over a period of 7 years (1995 - 2002).
