Recommendations for implementation and evaluation of Geographical Information Systems (GIS) can benfit from a broader theoretical foundation to support investigation, understanding and improvement. This paper discusses Actor-Network Theory (ANT) as a framework to delineate and evaluate the social and technical interactions involved in GIS implementation. The proposed process traces actor-network interactions through texts, technical objects, people, money and control. Actor alignment, actor-network stability and obligatory points of passage are evaluated to compare actor-networks. Case study research on conservation GIS implementation in Ecuador illustrates these methods. The strength of these actor-networks is examined through analysis of actors' interactions and the presence and function of an obligatory point of passage. Stronger actor-networks exhibit alignment among actors, co-location of an obligatory point of passage with the center of calculation and credit sharing.