BACKGROUND Early diagnosis and treatment of cancer is the goal of the 2-week-wait referral pathway (2WW). Variation exists between General Practice use of 2WW and rates of consultant reprioritisation of GP referral from routine to 2WW (Consultant Upgrade). We investigated variation in General Practice and Consultant Upgrade 2WW referral activity. METHODS Data from 185 000 referrals and 29 000 cancers recorded between 2011 and 2013 from the Northern Ireland Cancer Waiting Time database (CaPPS) were analysed to ascertain standardised referral rate ratios, detection rate (DR) (=sensitivity) and conversion rate (CR) (=positive predictive value) for Practice 2WW referrals and Consultant Upgrade 2WW. Metrics were compared using Spearman's rank correlation co-efficients. RESULTS There was consistency in Practice and Consultant Upgrade 2WW referral rates over time, though not for annual DR (Spearman's ρ<0.37) or CR (Spearman's ρ<0.26). Practice 2WW referral rates correlated negatively with CR and positively with DR while correlations between DR and CR were restricted to single-year comparisons in Practice 2WW. In Consultant Upgrade, 2WW CR and DR were strongly correlated but only when the same cancers were included in both rates. CONCLUSIONS Results suggest 'random case mix' explains previously reported associations between CR and DR with more 'hard to detect' cancers in some Practices than in others in a given year corresponding to lower DR and CR. Use of Practice and Consultant Upgrade 2WW referral metrics to gauge General Practice performance may be misleading.