Lantana camara L.var. aculeata, Parthenium hysterophorus (L.), Chromolaena adenophorum Spreng., Imperata cylindrica (L.) Beauv,Urtica dioca (L.) and Ageratum houstonianum (Mill.) are the major obnoxious perennial weeds of non-cropland hill ecosystems. These weeds are difficult to control and have spread like a wild fire in almost all the state because of the favourable climatic conditions, ability to propagate by seeds, stems and roots, faster dissemination by wind, water, birds, animals, machinery etc. and ability to adapt adverse conditions of hills. These weeds have become more problematic in hilly regions due to availability of more uncultivated land. These weeds are responsible to suppress useful vegetation in pasture and grasslands, orchards, forests, tea gardens, field bunds and other cropped and non-cropped lands by their competitive and allelopathic effects. These are responsible to threat plant biodiversity, shrinkage of grazing land, economic losses to the forest wealth, reduction in productivity of grasslands up to 90%. The toxins present in these weeds are proving hazardous to the health of animals and human beings. Preventive, mechanical, chemical, biological, utilization and integrated methods to manage these obnoxious perennial weeds have been discussed in this paper. These weeds should be cut at frequent intervals before flowering to exhaust food reserves in their vegetative propagules, check production of seeds and their dissemination. The cut biomass should be utilized to prepare compost, as mulch, biogas production, making furniture, as fuel wood and other industrial uses as per the property of weed species. A three phased integrated technology to manage Lantana camara under different hill ecosystems has been developed and demonstrated in large areas. In waste lands and forestland ecosystems, biological agents like Zygogramma bicolorata, Cassia tora or Cassia sericea are effective to manage Parthenium, hence should be introduced to check the rampant growth of this weed. In pasture and grasslands, herbicides should only be used in integration with plantation of fast growing forage species, recommended fertilizer, and harvesting or grazing schedules. These integrated technologies to manage Parthenium, Lantana and Ageratum have been demonstrated on large scale in hilly regions. However, for effective results, these technologies need to be adopted on campaign basis with the active participation of public, Government, scientists and policy makers.