Led by the hope of finding employment and education a growing number of people are drawn to the world's cities. Especially in the former colonial states of the southern hemisphere the urban population increased rapidly within a few decades. Due to the incapability of urban administrations and the asynchronous growth of infrastructure in relation to the population, squatter settlements and slums have evolved. Formal and informal districts became simultaneous urban realities. Yet, irregular structures show considerable spatial and infrastructural deficits. This thesis states the question with what means architects and planners can positively involve in the development of irregular settlements? With this premise, traditional methods of urban planning, the dichotomy of formal and informal city and the role of architects are reconsidered. This theoretical examination results in a three-step-process as a guideline for planning in irregular settlements. Attempts were further made to implement and evaluate this process with the case study Pasil in Cebu City in the Philippines. Detailed studies of spatial, cultural and socioeconomic aspects are the starting point and foundation of the planning process. Subsequently, catalogue-type premises were drafted. This permitted the development of site specific and needs-oriented proposals, which must be understood as concepts in the sense of urban acupunctures with catalysing effects.