By the year 2000, the number of people at risk from volcanic hazards is likely to increase to around half a billion. Since 1980, significant advances have been made in volcano monitoring, the data from which provides the sole scientific basis for eruption prediction. Here, internationally renowned and highly experienced specialists provide 25 comprehensive articles covering a wide range of related topics: monitoring techniques and data analysis; modelling of monitoring data and eruptive phenomena; volcanic hazards and risk assessment; and volcanic emergency management. Selected case histories of recent volcanic disasters, such as Mount Pinatubo in the Philippines, demonstrate that effective communication - between scientists, civil authorities, the media and the population at risk - is essential to reducing the danger.