We investigated what mobile workers do when they are mobile to achieve their communication goals, using contextual interviews and ethnographically inspired observations in a variety of settings. Implications for the design of mobile technology were extracted from the raw data collected in the fieldwork using such novel design techniques as `Day in the Life' vignettes, affinity diagrams, and consolidated artefact models from Contextual Design. Our findings are being using to generate software prototypes for supporting mobile activities. Keywords Mobile work, fieldwork, Contextual Design, prototyping