LONG-TERM MONITORING OF ACTIVE STARS .5. UBV(RI)(C) PHOTOMETRY COLLECTED IN FEB-MAR 1990

High-precision UBV(RI)(c) photometry of 12 selected active stars, coll ected at the European Southern Observatory (La Silla, Chile) over the period February - March 1990, is presented. Significant evolution of t he light curves, period variations and, in most cases, evidence for lo ng-term variability of the global degree of spottedness are found. Som e of the spectral classifications are discussed. This paper is part of a more extensive program focusing on the global properties and evolut ion of active stars and is aimed at establishing a time-extended photo metric database which can give important clues on topics such as the s tability of the spotted areas, differential rotation and solar-like cy cles.