Dubai Petroleum Company operates two large fields and several smaller ones in the Arabian Gulf. In developing these fields more than 40 separate production platforms have been set and several hundred wells drilled. As drilling has progressed, the Company has developed a series of drilling close rules to help prevent well collisions in these congested offshore production areas. This paper summarizes the evolution of the Company's collision avoidance work from the introduction of drilling close rules in the early 1980's to the present. Over this period Dubai Petroleum has moved from qualitative drilling close guidelines through a series of empirical rules to the current rules which are based on well specific error modelling and associated survey uncertainty checks. Development of the current rules using well collision probability modelling, economic analysis and detailed survey uncertainty comparisons is highlighted.