Background and Objectives:ATN (β-Amyloid, Tau, Neurodegeneration) system categorizes individuals based on their core Alzheimer’s disease (AD) biomarkers. An important potential future use for ATN is therapeutic decision-making in clinical practice once disease-modifying treatments, e.g., anti-amyloid, become widely available. In this cross-sectional study, we applied ATN and estimated potential eligibility for anti-amyloid treatment in a real-life memory clinic with biomarker assessments integrated into the routine diagnostic procedure and all specialized resources available for the implementation of novel treatments.Methods:We included all consecutive patients at the Karolinska University Hospital Memory clinic in Solna, Stockholm, Sweden, who had their first diagnostic visit in April 2018–February 2021, informed consent for the clinic research database, and available clinical and biomarker (CSF, imaging) data. ATN classification was based on CSF Aβ42 (or Aβ42/40; A), CSF phosphorylated tau (T), and medial temporal lobe atrophy (N). For CSF markers, we applied laboratory cut-offs and data-driven cut-offs for comparison (determined with Gaussian mixture modelling). Anti-amyloid treatment eligibility was assessed following the published recommendations for aducanumab (AD dementia or MCI with no evidence of non-AD etiology, appropriate level of cognition, AD-consistent CSF profile).Results:Study population consisted of 410 patients (52% subjective cognitive impairment, 23% mild cognitive impairment MCI, 25% any dementia; age 59±7 years, 56% women). Regardless of biomarker cut-offs, most patients were A−T−N− (54–57%). A+ prevalence was 17–30% (higher with data-driven cut-offs). Up to 13% of all patients (27% of those with MCI and 28% of those with dementia) were potentially eligible for anti-amyloid treatment when AD-consistent CSF was defined as any A+ profile. When A+T+ profile was required, treatment was targeted more to the dementia than MCI stage (eligibility up to 14% in MCI, 22% in dementia). The opposite applied to earlier stage intervention (A+T−N−; eligibility up to 12% in MCI, 2% in dementia).Discussion:In a memory clinic setting with all necessary infrastructure and national guidelines in place for dementia diagnostic examination (“best-case scenario”), most patients did not meet the eligibility criteria for anti-amyloid treatment. Continuing the development of disease-modifying treatments with different mechanisms of action is a priority.