Goitre prevalence and mental performance were determined amongst the Aborigines in Sinderut, a remote rural area in Pahang. A total of 196 subjects aged 4 to 60 years old were selected for study. Goitre status was determined by an experienced endocrinologist using classification suggested by World Health Organization; while mental performance was measured using Raven's test (Oxford Psychologists Press). Blood specimen was also taken for thyroxine (T4) and thyroid stimulating hormone (TSH) measurement. It was found that goitre prevalence was 26.5% (52/196); with visible goitre prevalence of 42.3% (22152). The overall mean of goitre volume was 21.4 ± 19.1 ml (range: 3.0 - 90.8 ml), while the prevalence of mental performance for the percentile value of more than 5.0 was 26.5% (range: 5.0 - 50.0). Mean thyroxine levels was 75.4 ± 19.3 nmol/L (range: 19.9 - 138.1 nmol/ L) while mean levels of thyroid stimulating hormone was 4.9 ± 3.2 mU/L (range: 0.4 - 18.9 mU/L). There was no significant correlation between hormone levels and mental performance score (Pearson Correlation; T4 : r=-0.002, p=0.9736; TSH : r=0.10, p=0.1843). goitre volume and mental performance score (Pearson Correlation; r=-0.02, p=0.8395). Goitre prevalence of more than 20% in this area indicates a moderate endemia, while mental performance showed a low thinking level in the Aborigines particularly those who lived in remote areas. Prevalens goiter dan performans mental telah ditentukan di kalangan penduduk Orang Asli di Sinderut; suatu kawasan pedalaman di Pahang. Seramai 196 subjek telah dipilih untuk kajian dengan julat umur dari 4 hingga 60 tahun. Status goiter telah ditentukan oleh pakar endokrinkologi menggunakan pengkelasan yang dicadangkan oleh Pertubuhan Kesihatan Sedunia; manakala performans mental diukur menggunakan ujian Raven (Oxford Psychologists Press). Pengambilan spesimen darah juga dilakukan untuk ditentukan paras tiroksin (T4) dan hormon perangsang tiroid (TSH). Didapati prevalens goiter adalah 26.5% (521196); dengan prevalens goiter nyata 42.3% (22152). Min isipadu goiter keseluruhan adalah 21.4 ± 19.1 ml (julat : 3.0 - 90.8 ml), sementara prevalens performans mental bagi nilai persentil lebih daripada 5.0 adalah 26.5% (julat : 5.0 - 50.0). Min paras tiroksin adalah 75.4 ± 19.3 nmol/L (julat : 19.9 - 138.1 nmol/L) manakala min paras hormon perangsang tiroid adalah 4.9 ± 3.2 mU/L (julat : 0.4 18.9 mU/L). Tidak terdapat korelasi yang signifikans di antara paras hormon dan skor performans mental (Korelasi Pearson; T4 : r=-0.002, p=0.9736; TSH : r=0.10, p=0.1843), serta isipadu goiter dan skor performans mental (Korelasi Pearson; r=-0.02, p=0.8395). Prevalens goiter 20% menunjukkan kawasan ini mengalami endemia yang sederhana. Performans mental pula menunjukkan tahap pemikiran yang rendah di kalangan penduduk Orang Asli terutamanya di kawasan pedalaman.