The present invention provides novel solid pharmaceutical dosage forms for oral administration, after being constituted in water. The solid dosage forms comprise a therapeutically effective amount of valganciclovir hydrochloride and a non-hygroscopic organic acid present in an amount sufficient to stabilize the valganciclovir hydrochloride in a predetermined amount of water. The present invention also provides novel liquid pharmaceutical dosage forms for oral administration after constituting the solid pharmaceutical dosage form with water. A non-hygroscopic bulking agent may optionally be included in the above dosage form. These novel pharmaceutical dosage forms are useful in the treatment or control of viruses such as herpes simplex virus and cytomegalovirus. The present invention also provides a method for treating these diseases employing the solid and liquid pharmaceutical dosage forms and a method for preparing these pharmaceutical dosage forms.