  We present time series data on the variable stars of the galactic globular
cluster Messier 3 (M3). We give BVI light curves for 226 RR Lyrae, 2 SX Phe and
1 W Vir type variables, along with estimated fundamental photometric parameters
such as intensity and magnitude-averaged brightness and pulsation periods. In
some cases the periods we have found significantly differ from the previously
published ones. This is the first published light curve and period
determination for variable V266. The I-band light curve has not been observed
previously for numerous (76) variables. Three new RR Lyrae variables have been
discovered. Groups of RR Lyrae variables that belong to different evolutionary
stages and have been separated previously on the basis of V data were found
here for all colours and colour indices by cluster analysis. The I-band period
-- luminosity relation is also discussed. From the 66 modulated (Blazhko type)
RR Lyrae stars we investigated, six are newly identified and two of them are
first overtone pulsators. In the case of 13 RR Lyrae, the period of Blazhko
cycle has been estimated for the first time. V252 is identified as a new RRd
variable. Amplitude ratio of RRd stars have been investigated to search
possible mode content changes. In contrast to previous publications no changes
have been found. Problems with the sampling of the time series of typical
cluster variability surveys is demonstrated.
