Gunasekaran et al (Pramana -J. Phys. 75 683-690 (2010)) report to have grown the nonlinear optical crystals urea thiourea mercuric chloride (UTHC) and urea thiourea mercuric sulphate (UTHS). We argue that UTHC and UTHS are dubious crystals and are not what the authors propose.Keywords: crystal growth; urea thiourea mercuric chloride; urea thiourea mercuric sulphate. CommentDuring the course of a literature survey of metal compounds containing both thiourea and urea ligands, the title paper by Gunasekaran et al [1] reporting on growth of so called urea thiourea mercuric chloride (UTHC) and urea thiourea mercuric sulphate (UTHS) crystals attracted our attention. For formulating these crystals, the authors did not take into consideration the known chemistry of Hg(II) towards thiourea

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