The aim of the study was to analyse the 2-year follow-up of a series of patients with the diagnosis of undifferentiated spondyloarthropathy (uSpA). A prospective study was carried out analysing 68 patients with symptomatic uSpA who fulfilled the European Spondylarthropathy Study Group (ESSG) criteria for seronegative spondyloarthropathies (SpA) and were aged between 18 and 50 years. Inclusion criteria included inflammatory low back pain (ILBP) (without radiographic sacroiliitis), asymmetric oligoarthritis (predominantly affecting large joints in the lower limbs) and heel enthesopathies (Achilles tendinitis and/or plantar fasciitis). Imaging methods included pelvic radiography (at study entry and after 2 years) and calcaneal radiography (at study entry). There was a predominance of male gender (78%), caucasoid race (72%) and positive HLA-B27 (54%), with a mean age of 31 years and mean disease duration of 5 years. The first disease manifestations were ILBP (49%), asymmetric oligoarthritis (35%) and heel enthesopathies (16%). A positive family history of a definite SpA was mentioned by 9% of the patients. Seventeen patients (25%) scored 5 points in the Amor set of SpA criteria; logistic regression analysis showed that HLA-B27, heel enthesopathy and asymmetric oligoarthritis were significantly associated with Amor criteria > or = 6, whereas ILBP was associated with Amor criteria <6. Male sex was associated with heel enthesopathies (p = 0.041) and ankle involvement (p = 0.015). Caucasoid race was associated with ILBP (p=0.015) and buttock pain (p = 0.047). Positive HLA-B27 was associated with wrist involvement (p=0.019) and Amor criteria > or = 6 (p=0.001). After a 2-year follow-up the following outcomes were observed: uSpA 75%; disease remission 13%; ankylosing spondylitis 10%; psoriatic arthritis 2%. Logistic regression analysis showed that buttock pain and positive HLA-B27 (trend) were statistically associated with progression to a definite SpA. In conclusion, uSpA can represent a provisional diagnosis in the group of SpA and a systematic follow-up is necessary in order to better establish the different patterns of the disease.