OBJECTIVES Sleep apnoea is common in active acromegaly. It is associated with increased morbidity and mortality but can be treated effectively. The objective of this study was to determine the largely unknown relative frequency of, and the predictive factors for, sleep apnoea in treated acromegalic patients.DESIGN Retrospective cohort study.SETTING Tertiary referral hospital.PATIENTS Fifty‐four of 100 patients with treated acromegaly. If sleep apnoea had been diagnosed before acromegaly, the patient was excluded.MEASUREMENTS Sleep studies (using the MESAM‐4 device measuring oxyhaemoglobin saturation, heart rate, snoring sounds and body position to determine presence and severity of sleep apnoea); GH and IGF‐I levels; body mass index, neck and index‐finger circumference; daytime symptoms of sleep apnoea, duration of acromegaly before treatment, shoe and neck‐size difference since beginning of acromegaly; age, sex and treatment modes of acromegaly.RESULTS The relative frequency of sleep apnoea was 39% in the 54 patients with sleep studies and at least 21% in the entire study population of 100 patients.In patients with sleep apnoea, statistically significant higher values were observed for GH (P = 0.002), IGF‐I (P = 0.029), age (P = 0.014) and neck circumference (P = 0.016). An index‐finger circumference of ≥8.5 cm was associated with a significantly higher desaturation index (P = 0.012, Mann–WhitneyItest). Adenomectomy had been performed significantly less frequently in patients with sleep apnoea (P < 0.001, χ2test). The body mass index was non‐significantly higher in the patients with sleep apnoea.CONCLUSIONS The relative frequency of sleep apnoea in patients with treated acromegaly is at least 21%. Parameters of predictive value for the presence of sleep apnoea in this population are neck and index‐finger circumference as measures of soft tissue hypertrophy, age, GH and