| X Chromosome |
| X Chromosome Inactivation |
| X Chromosome, Human use Chromosomes, Human, X |
| X Inactivation use X Chromosome Inactivation |
| X-Chromosome Genes use Genes, X-Linked |
| X-Linked Adrenoleukodystrophy use Adrenoleukodystrophy |
| X-Linked Combined Immunodeficiency Diseases |
| X-Linked Genes use Genes, X-Linked |
| X-Linked Genetic Diseases use Genetic Diseases, X-Linked |
| X-Linked Inhibitor of Apoptosis Protein |
| X-Linked Juvenile Retinoschisis use Retinoschisis |
| X-Linked Lymphoproliferative Syndrome use Lymphoproliferative Disorders |
| X-Linked Mental Retardation use Mental Retardation, X-Linked |
| X-Linked Retinoschisis use Retinoschisis |
| X-Linked Severe Combined Immunodeficiency use X-Linked Combined Immunodeficiency Diseases |
| X-Linked Traits use Genes, X-Linked |
| X-Linked, Spastic Paraplegia, Hereditary use Spastic Paraplegia, Hereditary |
| X-Ray (Homeopathy) |
| X-Ray Absorptiometry use Absorptiometry, Photon |
| X-Ray Absorption Spectroscopy |
| X-Ray Crystallography use Crystallography, X-Ray |
| X-Ray Departments use Radiology Department, Hospital |
| X-Ray Diffraction |
| X-Ray Emission Spectrometry use Spectrometry, X-Ray Emission |
| X-Ray Emission Spectrometry, Electron Microscopic use Electron Probe Microanalysis |
| X-Ray Emission Spectrometry, Electron Probe use Electron Probe Microanalysis |
| X-Ray Emission Spectroscopy use Spectrometry, X-Ray Emission |
| X-Ray Film |
| X-Ray Film-Screen Systems use X-Ray Intensifying Screens |
| X-Ray Fluorescence Spectrometry use Spectrometry, X-Ray Emission |
| X-Ray Information Systems use Radiology Information Systems |
| X-Ray Intensifying Screens |
| X-Ray Microanalysis, Electron Microscopic use Electron Probe Microanalysis |
| X-Ray Microanalysis, Electron Probe use Electron Probe Microanalysis |
| X-Ray Microtomography |
| X-Ray Therapy |
| X-Ray Tomography use Tomography, X-Ray |
| X-Ray Tomography, Computed use Tomography, X-Ray Computed |
| X-Ray, Diagnostic use Radiography |
| X-Rays |
| Xamoterol |
| Xanthacridinum use Acriflavine |
| Xanthenes |
| Xanthine |
| Xanthine Dehydrogenase |
| Xanthine Oxidase |
| Xanthines |
| Xanthinol Niacinate |
| Xanthinol Nicotinate use Xanthinol Niacinate |
| Xanthium |
| Xanthium spinosum |
| Xanthobacter |
| Xanthobacter autotrophicus use Xanthobacter |
| Xanthobacter flavus use Xanthobacter |
| Xanthoceras use Sapindaceae |
| Xanthogranuloma, Juvenile |
| Xanthogranulomatous Pyelonephritis use Pyelonephritis, Xanthogranulomatous |
| Xanthoma use Xanthomatosis |
| Xanthoma Disseminatum use Histiocytosis, Non-Langerhans-Cell |
| Xanthoma, Juvenile use Xanthogranuloma, Juvenile |
| Xanthomatosis |
| Xanthomatosis, Cerebrotendinous |
| Xanthomatosis, Familial use Wolman Disease |
| Xanthomatosis, Wolman's use Wolman Disease |
| Xanthomonadaceae |
| Xanthomonas |
| Xanthomonas albilineans use Xanthomonas |
| Xanthomonas axonopodis |
| Xanthomonas campestris |
| Xanthomonas maltophilia use Stenotrophomonas maltophilia |
| Xanthomonas vesicatoria |
| Xanthones |
| Xanthophylls |
| Xanthopterin |
| Xanthorhiza |
| Xanthorrhiza apifolia |
| Xanthorrhoea arborea |
| Xanthosoma |
| Xanthotoxin use Methoxsalen |
| Xanthoxylum use Zanthoxylum |
| Xanthoxylum americanum use Xanthoxylum fraxeneum |
| Xanthoxylum fraxeneum |
| Xanthurenates |
| Xantinol Nicotinate use Xanthinol Niacinate |
| Xedar Receptor |
| Xenarthra |
| Xenoantibodies use Antibodies, Heterophile |
| Xenoantigens use Antigens, Heterophile |
| Xenobiotics |
| Xenodiagnosis |
| Xenograft Antitumor Assays use Xenograft Model Antitumor Assays |
| Xenograft Bioprosthesis use Bioprosthesis |
| Xenograft Dressings use Biological Dressings |
| Xenograft Model Antitumor Assays |
| Xenon |
| Xenon Chloride Excimer Lasers use Lasers, Excimer |
| Xenon Ion Lasers use Lasers, Gas |
| Xenon Isotopes |
| Xenon Radioisotopes |
| Xenopsylla |
| Xenopus |
| Xenopus laevis |
| Xenopus laevis Proteins use Xenopus Proteins |
| Xenopus Proteins |
| Xenorhabdus |
| Xenorhabdus luminescens use Photorhabdus |
| Xenorhabdus nematophila use Xenorhabdus |
| Xenotransplantation use Transplantation, Heterologous |
| Xenotropic MuLV-related virus use Xenotropic murine leukemia virus-related virus |
| Xenotropic murine leukemia virus-related virus |
| Xeroderma use Ichthyosis |
| Xeroderma Pigmentosum |
| Xeroderma Pigmentosum Group A Protein |
| Xeroderma Pigmentosum Group D Protein |
| Xeromammography |
| Xerophthalmia |
| Xerophyllum |
| Xeroradiography |
| Xeroradiography, Breast use Xeromammography |
| Xerostomia |
| Xestospongia |
| Xiakucao use Prunella |
| Ximenia use Olacaceae |
| Xipamide |
| Xipapillomavirus |
| Xiphoid Bone |
| Xiphophorus use Cyprinodontiformes |
| Xiphosura use Horseshoe Crabs |
| Xiphosura americana |
| XMRV Virus use Xenotropic murine leukemia virus-related virus |
| Xylamide use Proglumide |
| Xylan Endo-1,3-beta-Xylosidase |
| Xylans |
| Xylariales |
| Xylazine |
| Xylella |
| Xylem |
| Xylenes |
| Xylitol |
| Xylobiases use Xylosidases |
| Xylopia |
| Xylose |
| Xylosidases |
| Xylulose |
| XYY Karyotype |
