Dedicated to Prof György Keglevich on the occasion of his 65 th birthday.Paracetamol and valproic acid are standalone drugs with leading position in the world drug market. The phosphonate analogues of these drugs were synthesized and were tested in vivo. N-(4-hydroxyphenylcarbamoyl)phosphonic acid was four times more potent than paracetamol in preventing acetic acid-induced writhing. Phosphonate derivative of valproic acid, (2propylpentanoyl)phosphonic acid, had similar in vivo activity to valproic acid in the pentylenetetrazole-induced kindling mouse model.