The aim of this study was to compare the effect of nasally administered glucagon in doses of 1 (A) and 2 mg (B), with 1 mg glucagon administered intramuscularly (C) in 12 C-peptide-negative IDDM patients. Spontaneous recovery (D) from insulin-induced hypoglycaemia in the same patients was used as reference. The mean age was 31.1 (21-48) years, diabetes duration 10.8 (2.7-31) years and HbA1c 7.7 (6.5-9.8)%. Hypoglycaemia was induced by i.v. insulin infusion. When blood glucose (BG) reached about 2 mmol/l either glucagon was administered or the patients recovered spontaneously. BG nadir was 1.6 (1.1-2.3) mmol/l. BG increments during the first 15 min after glucagon administration were: (A) 1.9 +/- 0.7 (0.4-3.0); (B) 2.5 +/- 0.7 (1.5-3.5); (C) 2.5 +/- 1.0 (1.2-4.7); and (D) 0.3 +/- 0.4 (0-1.0) mmol/l, respectively. All treatments were more effective, measured as increments in BG, than spontaneous recovery, P less than 0.00001. There was no difference between nasal treatment with 2 mg (B) and i.m. treatment (C), both being more effective than 1 mg (A) nasal treatment, P less than 0.1. BG continued to increase up to 10 mmol/l 90 min after i.m. glucagon administration, whereas it stabilized at a level of 4.6-6 mmol/l, 30-45 min after nasal administration. Eighty percent of the patients had side-effects to nasal administration - local irritation, rhinitis or sneezing. Half of the patients sneezed, without correlation with the delivered dose of glucagon. None of the patients had side-effects which would preclude further treatment.(ABSTRACT TRUNCATED AT 250 WORDS)