INTRODUCTION The sub-clinical mastitis is an inflammation of the udder usually associated with a microorganism. The appearance of milk and gland itself is not impaired, but there are changes in the milk composition. The prevalence of clinical mastitis is less than 5% in goats, while the sub- clinical mastitis are much more common with a prevalence which ranges from 18 to 34% (Bauer et al., 1997; Bergonier, 1997; Chingwen et al., 2002). Among the most used for the diagnosis of subclinical mastitis methods, the CMT (Clifornian Mastitis Test). AIMS AND OBJECTIVES Our research aims to determine the prevalence of subclinical mastitis in local goats in Laghouat region (ALGERIA). MATERIALS AND METHODS The experimental herd consists of 60 goats aged 1 to 9 years old, weighing 18 to 45 kg live weight and whose lactation number varies from 2 to 8. The screening for subclinical mastitis is performed by the Califirnian Mastitis Test (CMT). The manner of interpretation of CMT results is as follows: See the degree of gelation (formation Prevalence of Subclinical Mastitis in the Local Goats in the Province of Laghouat (ALGERIA) Achour YAHIA 1 *, Djelloul MREZGUI 1 , Khadidja HAMRAT 2 and Rachid KAIDI 1 1 Laboratory of Biotechnology related to Animal Reproduction, Veterinary Sciences Institute, University of Blida 1. Algeria. 2 Directorate of Agricultural Services, Blida. Algeria achourveto@yahoo.fr Bulletin UASVM Veterinary Medicine 73(2) / 2016, Print ISSN 1843-5270; Electronic ISSN 1843-5378 DOI:10.15835/buasvmcn-vm: 12169 Abstract Subclinical mastitis is a disease of the udder that passes mostly unnoticed. Or several germs associated with it and their presence in milk constitutes a major risk to consumer health. Our study aims to determine the prevalence of subclinical mastitis in local goats in Laghouat region (Algeria). We undertook a study based on the detection of sub-clinical mastitis by Califirnian Mastitis Test (CMT) in 60 goats aged 1 to 9 years and weighing 18 to 45 kg of live weight and whose lactation number varies from 2 to 8. We found a prevalence of subclinical mastitis reaching 46.6%. A clearly significant difference (P <0.05) is reported on this prevalence compared to age. The highest rate is recorded especially in goats aged between 3 to 7 years with 62% of detected subclinical mastitis, followed by the older goats (over 7 years) with a prevalence of 27%, and at the end the youngest goats (1-3 years) with a prevalence of 11%. A significant difference was also recorded between the different lactation ranks (P <0.05). The goats having the highest rank of lactation were most affected by subclinical mastitis. Prevalence of 46%, 31%, 11% and 8% respectively are found for the 6 th rank of lactation and more, 4 lactations, 5 lactations and 1 lactation. We noticed that the majority of diagnosed mastitis were caused by poor hygiene conditions. This study allows us to conclude that there is a high prevalence of subclinical mastitis in the local goats in the province of Laghouat (Algeria). Keywords: goats, prevalence, sub-clinical mastitis.