The use of prescription drugs in older people is high and many commonly prescribed drugs have anticholinergic effects. We examined the relationship between ACB on mortality and in-patient length of stay in the oldest old hospitalised population. This was a retrospective analysis of prospective audit using hospital audit data from acute medical admissions in three hospitals in England and Scotland. Baseline use of possible or definite anticholinergics was determined according to the Anticholinergic Cognitive Burden Scale. The main outcome measures were decline in-hospital mortality, early in-hospital mortality at 3- and 7-days and in-patient length of stay. A total of 419 patients (including 65 patients with known dementia) were included [median age=92.9, inter-quartile range (IQR) 91.4-95.1 years]. 256 (61.1%) were taking anticholinergic medications. Younger age, greater number of pre-morbid conditions, ischemic heart disease, number of medications, higher urea and creatinine levels were significantly associated with higher total ACB burden on univariate regression analysis. There were no significant differences observed in terms of in-patient mortality, in-patient hospital mortality within 3- and 7-days and likelihood of prolonged length of hospital stay between ACB categories. Compared to those without cardiovascular disease, patients with cardiovascular disease showed similar outcome regardless of ACB load (either =0 or >0 ACB). We found no association between ACB and early (within 3- and 7-days) and in-patient mortality and hospital length of stay outcomes in this cohort of oldest old in the acute medical admission setting.