The paper summarizes results of the study of the occurrence, development and harmfulness of Phratora (= Phyllodecta) vitellinae (L.). The majority of studies was carried out in 1998 to 2005 in riparian and accompanying stands of the Svitava and Svratka rivers in the region of Brno and in a laboratory. Imagoes leave hibernation hiding places at the end of April and at the beginning of May. In captivity, they lived on Salix fragilis about 2.5 months damaging on average 28.6 cm² leaf blades and laying on average 293 eggs. In the excessively warm growing season of 2005, imagoes lived about 3.5 months after hibernation, however, already after one month of feeding they fell in a month diapause at the beginning of June. Before its start, they damaged on average 12.8 cm² (after the diapause 14.4 cm²) leaves and laid on average 389 eggs (of this number, 260 eggs before and 129 after the diapause). Larvae damage about 4 cm² leaves during 2 to 3 weeks (in the laboratory during 12 to 13 days). After 2 to 3 weeks (in the laboratory after 10 to 12 days) from the cessation of feeding young beetles appear on trees. Imagoes of the 1^st generation occur from mid-June to the beginning of October. During about 55 days of life, they damaged 19 cm² leaves and laid on average 182 eggs. Imagoes of the 2^nd generation occur from mid-August to the end of the growing season. After 10 to 14 days of feeding (without previous copulation), they take shelter in wintering places. In the laboratory, however, these imagoes damaged about 19 cm² leaves during 2 months and laid about 190 eggs. Wintering places were looked up by imagoes of the 3^rd generation which damaged on average 4.2 cm² leaves before hibernation. In the Czech Republic, P. vitellinae is usually bivoltine the 2^nd generation being always incomplete.