This thesis comprises a systematic literature review and empirical paper investigating observational coding systems that have been applied to study interactions between couples where one spouse has a diagnosis of a chronic condition. The literature review offers a critical evaluation of nine coding systems that have been used by 14 papers. A description of each coding system is provided, as well as its theoretical development, evaluation of its application, reliability, validity, generalizability, and utility with a chronic condition population. The review concludes that tailored coding systems need to be developed that focus on specific behaviours that would inform care of someone with a chronic condition.The empirical paper presents the development and psychometric evaluation of an observational coding system for person-centred spousal care. Eleven couples, where one spouse had a diagnosis of dementia, were video-taped completing an everyday task. These videos were coded by three trained raters. Care-giving spouses also completed the Birmingham Relationship Continuity Measure as a measure of relationship continuity. Results suggested that the coding system had good inter-rater reliability, although validity needs to be evaluated. The hypothesis, that spouses scoring high on relationship continuity would relate using a more person-centred approach, was not supported.