The nature of advertising creativity is explored as a professional, applied creative service product, within a business-to-business context. Findings are reported from a series of extensive in-depth interviews with advertising managers in major client organisations. Analysis of these interviews generated a detailed conceptualisation of the advertising problem delineation, communication and response (APDCR) process, expressed in a flowchart. The data also suggest two variations in the pattern of agency-client relationships within which the APDCR process operates, and factors that may be responsible for these variations. A better understanding of the nature and dynamic operation of creative service may enable both agency and advertiser stakeholders to achieve greater satisfaction.