Isotopic dating of 32 whole rock samples from seven of the Papua New Guinea highlands volcanoes shows a wide spread of ages ranging from 1.6 m.y., or possibly 1.9 m.y., to around 200 000 years B.P. These dates, with evidence of recent activity on two volcanoes, suggest that the highlands volcanic province has been active for at least the last 1.6 million years and that early volcanism was contemporaneous with intrusive igneous activity in the Star Mountains. Major eruptions of lavas, however, ceased at about 200 000 years B.P. and there is evidence from some of the volcanoes of apparent long breaks in activity.