BACKGROUND: Cerebrospinal fluid (CSF) biomarkers β-amyloid 1-42 (Aβ1-42), also expressed as Aβ1-42:Aβ1-40 ratio, T-tau, and P-tau181P, have proven diagnostic accuracy for mild cognitive impairment and Alzheimer's disease (AD). How to use, interpret, and disclose biomarker results drives the need for standardization. METHODS: Previous Alzheimer's Biomarkers Standardization Initiative meetings discussed preanalytical issues affecting Aβ1-42 and tau in CSF. This second round of consensus meetings focused on issues related to clinical use of AD CSF biomarkers. RESULTS: Consensus was reached that lumbar puncture for AD CSF biomarker analysis be considered as a routine clinical test in patients with early-onset dementia, at the prodromal stage or with atypical AD. Moreover, consensus was reached on which biomarkers to use, how results should be interpreted, and potential confounding factors. CONCLUSIONS: Changes in Aβ1-42, T-tau, and P-tau181P allow diagnosis of AD in its prodromal stage. Conversely, having all three biomarkers in the normal range rules out AD. Intermediate conditions require further patient follow-up.