['Hypertension is an important complication of multicystic dysplastic kidney and it has been suggested that it is induced by renin. Little information is available on renin production in this disease. To assess renin production we examined the distribution of renin containing cells in multicystic dysplastic kidneys using immunohistochemical methods.', 'Immunohistochemical examination of renin was performed in 29 multicystic dysplastic kidneys from 14 boys and 15 girls 1 month to 10 years old using rabbit anti-human renin antibodies. In all cases normal renal function was confirmed by the serum creatinine level and no proteinuria on urinalysis. Two patients had the complication of hypertension before removal of the multicystic dysplastic kidney but plasma renin activity was normal.', "Immunostaining of renin was observed in 26 of 29 multicystic dysplastic kidneys (90%). Histologically multicystic dysplastic kidney involved scarred and dysplastic areas. Renin positive cells were observed predominantly in the scarred areas, mainly in the juxtaglomerular apparatus of mature glomeruli, interlobular arteries and some mature tubules. Immunopositive renin was sparsely noted in the juxtaglomerular apparatus or Bowman's capsules of occasional immature glomeruli in dysplastic areas."] Are renin containing cells present predominantly in scarred areas but not in dysplastic regions in multicystic dysplastic kidney?