A 32-year-old woman first had thyrotoxicosis and severe pernicious anemia (PA) in 1975. The initial serum thyroxine (T4) level, 14.5 microgram/dL, rose to 29.2 microgram/dL, with no other therapy except cyanocobalamin injection and blood tranfusions. She again had thyroid storm and PA in 1978. The serum T4 level was only slightly elevated, but the triiodothyronine (T3) level was normal. She received therapy for both diseases and recovered. Four months later, with a normal hematocrit reading, thyrotoxicosis recurred, with noticeable elevation of T4 and T3. These data suggest that first, thyroid storm can occur with excess T4 only, and its occurrence does not depend on the degree of thyroid hormone elevation; and second, thyroid hormone level may be depressed in severe PA, and a normal T3 level should not rule out thyrotoxicosis in this condition.