Objective. To address the issue of diagnostic delay in Duchenne Muscular Dystrophy (DMD) using developmental data from a cohort of affected boys detected by newborn screening and data on the diagnostic pathways of a group of boys diagnosed clinically. Design. Quantitative and semi-qualitative. Setting. Primary Care Subjects. 1. Cohort of boys diagnosed by newborn screening (NBS cohort) 2. Group of mothers whose sons were diagnosed clinically (LCD group) Interventions. NBS cohort: (a) Developmental milestones, (b) Griffiths assessment, (c) clinic letters, (d) family case studies. LCD group: semi-structured interview. Main outcome measure. 1. The effectiveness of previously proposed strategies for the earlier clinical diagnosis of DMD. 2. Diagnostic pathways of the LCD group. Factors contributing to diagnostic delay in the LCD group. Results. 1. Previously proposed strategies for earlier diagnosis would have had limited effectiveness in detecting the NBS cohort. 2. Diagnostic delay continues because: (a) initial observations are usually non-specific and made by the family, (b) age of presentation and presenting symptoms are highly variable, (c) first concerns are usually expressed to the primary care team who are less likely to recognise the early indicators, (d) early locomotor symptoms could suggest an orthopaedic rather than a paediatric referral. Conclusions. The identification and implementation of an effective screening tool to reduce diagnostic delay is more complex than previously portrayed. In the light of this evidence service providers need to ask whether newborn screening is the only feasible solution to diagnostic delay.