Shrimp aquaculture is one of the growing animal industries. Breeding stocks with high disease-resistance and growth rate are of particular interest to shrimp breeders. Association studies are useful to find genetic markers for marker assisted selection of animals. Using six Litopenaeus vannamei individuals from a sample population, four single nucleotide polymorphisms (SNPs) were found in the 5HT1R (5-hydroxytryptamine receptor1) gene and one SNP in the STAT (signal transducer and activator of transcription) gene. However, the SNP in the STAT gene was homozygous in a different population used for association analyses. The association analyses revealed that allele C of two SNPs, C109T and C395G in 5HT1R, tended to be associated with increased body weight. Further studies need to be conducted using a large and diverse population sample.