A once-a-day controlled release diltiazem formulation is described which includes: (a) from 20 to 50 % by weight of enteric polymeric membrane coated pellets comprising a polymer membrane coated core which comprises a biologically inert core which is coated with a first layer which consists essentially of diltiazem and a polymeric binder; and a second layer which comprises a membrane comprising a pH dependent polymeric material; and (b) from 50 % to 80 % by weight of delayed pulse polymeric membrane coated pellets comprising a polymeric membrane coated core which comprises a biologically inert core which is coated with a first layer which consists essentially of diltiazem and a polymeric binder and a second layer which comprises a polymeric membrane which will substantially maintain its integrity in the varying pH conditions of the gastrointestinal tract but is permeable to diltiazem; and (c) a unit dose containment system.