The use of a 50percent citric acid cleanser in root canals after pulpectomy produced well-cleaned surfaces as shown by scanning electron microscopy. Compared with other cleaning agents, this cleanser provided improved penetration of rosin into the dentinal tubules and better wall adaptation of gutta-percha. No contraindication has been encountered in clinical practice. Application of the cleanser directly to the exposed pulp resulted in satisfactory destruction similar to the results obtained with strong acids.