15 letters
- protozoologists30
- psychohistorian28
- psychohistories27
- psychotomimetic34
- radioautographs24
- radioautography26
- rechromatograph30
- reflectometries25
- refractometries24
- rephotographing30
- retinoblastomas23
- retroperitoneal20
- retroreflectors22
- rheumatologists24
- schistosomiases23
- schistosomiasis23
- sedimentologies23
- sedimentologist23
- serendipitously24
- sociohistorical24
- spermatogeneses24
- spermatogenesis24
- splenectomizing38
- stockbrokerages31
- stoichiometries23
- stratovolcanoes24
- streptobacillus27
- streptothricins24
- superconductors28
- sympathectomies31
- symptomatically33
- symptomatologic32
- telephotography30
- teratocarcinoma25
- territorialisms19
- territorialists16
- territorialized26
- territorializes25
- tetragrammatons24
- thermoreceptors26
- thermoregulator24
- thyrocalcitonin28
- thyroidectomies26
- toastmistresses18
- tomboyishnesses26
- tonsillectomies24
- toothsomenesses21
- topographically32
- totalitarianism20
- totalitarianize26
- toxicologically35
- transhistorical22
- transistorising19
- transistorizing28
- trinitrotoluene19
- turbogenerators22
- ultramicrotomes26
- vasoconstrictor26