Physical rehabilitation day hospitals are widely used community-based services designed to meet the medical and rehabilitation needs of older people. While there is evidence for the effectiveness of these services, concerns about the shortcomings of how this is measured have led to the recommendation that the achievement of individually tailored goals be used to assess outcomes. This study considered whether such goal achievement demonstrated validity with respect to a standardised measure. The association between goal achievement and change in Nottingham Health Profile-Part 1 (NHP-1) scores was considered for 102 people attending four physical rehabilitation day hospitals. The predicted significant positive relationship between the percentage of goals achieved by participants and NHP-1 scores was not found. This remained evident when functional goals were considered separately to medical goals. Further subsidiary analyses identified a complex relationship between goal achievement and NHP-1 change scores. For those with higher change scores, there was a significant negative association between NHP-1 change and goal achievement; while for those with lower (or negative) change scores, there was a significant positive association. A curve estimate regression confirmed a highly significant quadratic (curvilinear) relationship. Possible reasons for this finding might include the timing and nature of the goals set, the potential complication of some participants having cognitive impairment, as well as the use of the NHP-1 as a comparison measure. At this time it is recommended that goal achievement only be used alongside other measures of day hospital outcome. (Contains 2 tables and 1 figure.)