Trends in adolescent suicide rates (15-19 years) from 1979 to 1996 were compared with suicide trends in individuals of 20 years and over in 30 countries and with trends in rates of deaths due to undetermined causes in adolescents in 17 countries of the WHO European Region. In 21 of the 30 studied countries, male adolescent suicide rates increased during the study period (highest increases in Belarus, Kazakstan and Ireland) accompanied by far less increases or decreases in suicide rates of males of 20 years and over. Part of the observed increases in Sweden, Ireland and Greece can be attributed to improved suicide statistics, while increases in Finland, Belgium, Bulgaria and the United Kingdom can be even higher due to the rising classification of deaths as "undetermined". In Portugal, decreasing suicide trends seem to be misinterpreted by ignoring the vast increases in rates of undetermined deaths. Female adolescent suicide rates rose less markedly than in males in 18 countries, with the exception of strong increases in Norway, Ireland. Increases in female adolescent suicide rates were marginally affected by changes in classification practices and were accompanied primarily by declining suicide rates in females of 20 years and over.