The 1,3-dipolar cycloaddition of nitrile imines to 9 H-thioxanthone-9-thione and 9 H-xanthone-9-thione afforded novel spiro-thioxanthene-9′,2-[1,3,4]thiadiazoles 6a– g and spiro-xanthene-9′,2-[1,3,4]thiadiazoles 7a– g in good yields. Some of the newly synthesized compounds were tested for anti-inflammatory and analgesic activities comparable to ibuprofen. Compounds 6a, d, e and 7a, d, e showed significant activity compared to standard drug. The toxicity studies revealed that neither death nor other behavioral or toxicological changes were observed on rats up to a dose as high as 200 mg/kg.