Narcolepsy-Cataplexy (NC) is a neurological disorder associated with the human leukocyte antigen HLA DR2. This is a prerequisite for the disease in 95 to 98% of Caucasian patients. It has been demonstrated that the HLA DQB1*0602 allele is a better marker for narcolepsy than DRB1*1501 (DR2). We present a DR-negative and DQB1*0602-positive Caucasian Spanish patient with a very unusual genotype. A 20-year-old male presented with a 12-year history of excessive daytime sleepiness and sudden muscle weakness caused by laughter and disturbed nocturnal sleep. He had never presented hypnagogic hallucinations or sleep paralysis. The family history was negative. Physical and neurological examinations were normal. The Epworth Sleepiness Scale score was 21/24, The Ullanlinna Scale score was 20/40. The polysomnographic recording showed short sleep latency, increased percentage of stage 1 (St 1), increased number of body movements and decreased sleep efficiency index. MSLT data: mean sleep latency of 1 minute and three sleep onset rapid eye movement (REM) periods (SOREMPs). HLA phenotype: A1, A11; Cw5, Cw7; B44, B39; Bw4, Bw6; DR4, DR8; DR53; DQ6, DQ8 and at the gene level: DRB1*0402, DQB1*0302; DRB1*0806, DQB1*0602. The DRB1*0806 and DQB1*0602 genotype is very infrequent in NC and identical to one African-American case in the series by Mignot et al. (1997a), and to a Caucasian case in another series by Mignot et al. (1997b). This indicates the genetic heterogeneity of the NC.