We describe two cases in which dynamic analysis of ejaculation using color Doppler ultrasonography was useful in diagnosis of ejaculatory dysfunction and planning of therapy. The first patient was a 32-year-old man with a diagnosis of retrograde ejaculation. A bladder neck collagen injection was carried out, as the main cause was thought to be the bladder neck remaining open during ejaculation. The patient had antegrade ejaculation 1 week later. The second patient was a 48-year-old man with a diagnosis of anorgasmia accompanied by decreased seminal emission and insufficient function of the rhythmic pelvic striated muscles. The patient was prescribed etilefrine hydrochloride 15 mg/day. The symptom improved 2 weeks after starting this drug. These cases suggest that the use of color Doppler ultrasonography during ejaculation can improve the understanding of ejaculatory dysfunction and therapy for this condition.