OBJECTIVE: To investigate tolerability and glycemic control over 26 weeks in patients with type 2 diabetes (T2D) who initiated insulin with, or switched to, biphasic insulin aspart 30/70 (BIAsp 30) in routine clinical care. METHODS: This was a non-randomized, non-interventional, open-label, observational study involving patients under the care of approximately 150 insulin-prescribing physicians in Denmark. All patients enrolled were prescribed BIAsp 30 in routine care. Starting dose, dose titration and injection frequency were determined individually by each physician. Information on serious adverse drug reactions (SADR), glycemic parameters and hypoglycemic events were obtained from patients’ notes, patients’ diaries and recall, and transferred to case report forms by physicians at baseline (during 4 weeks prior to BIAsp 30 therapy) and after 12 and 26 weeks of treatment. RESULTS: 421 subjects were recruited and 392 provided safety data. The age (mean ± SD) was 62.0 ± 11.4 years, body mass index (BMI) 30.4 ± 6.4 kg/m2, duration of diabetes 9.1 ± 8.1 years and HbA1c (%) 9.4 ± 1.7. 199 subjects were prior insulin users and 193 were insulinnaïve patients. Four patients reported a SADR (3 hypoglycemia, 1 severe hypoglycemia). HbA1c was significantly reduced after 26 weeks of BIAsp 30 therapy: prior insulin users -1.2%, insulin-naïve patients -2.2% (both p < 0.001). 28% and 41% of patients, respectively, reached target HbA1c < 7%. Overall the hypoglycemia rate was lower for insulin-naïve patients than for prior insulin users: 5.0 vs. 6.6 episodes/patient-year (p < 0.05). CONCLUSION: Initiating insulin with, or switching insulin to, BIAsp 30 in routine care was safe and effective in patients with T2D.