The absence of iodine uptake in metastases of differentiated thyroid carcinoma makes them unresponsive to treatment with radioiodine 131I. In many of such cases symptomatic treatment remains the only available therapy. The results of studies on partial redifferentiation of metastases of thyroid cancer achieved after cis-retinoid acid therapy have drawn attention to the possibility of restoration of iodine uptake in metastases after pretreatment with cis-retinoic acid (Roaccutane). 5 patients with iodine uptake-negative metastases of differentiated thyroid carcinoma were given Roaccutane in a dose 1.5 mg/kg/24 h daily for 6 weeks before the therapy with radioiodine. In none of the patients restoration of radioiodine uptake in metastases has occurred as shown in post-therapeutic total body scintigraphy.