Identifying patients with pulmonary fibrosis (PF) at risk of progression can guide management. We explore the utility of combining baseline bronchoalveolar lavage (BAL) and CT in differentiating progressive and non-progressive PF. The derivation cohort consisted of incident cases of PF, for whom BAL was performed as part of diagnostic work-up. A validation cohort were prospectively recruited with identical inclusion criteria. Baseline thoracic CTs were scored for fibrosis extent and UIP pattern. BAL lymphocyte proportion was recorded. Annualized forced vital capacity decline >10% or death within one year defined disease progression. Multivariable logistic regression identified determinants of outcome. Optimum binary thresholds (maximal Wilcoxon rank statistic) at which CT fibrosis extent and BAL lymphocyte proportion could distinguish disease progression were identified. BAL lymphocyte proportion, UIP pattern and fibrosis extent were significantly and independently associated with disease progression in the derivation cohort (n=240 individuals). Binary thresholds for raised BAL lymphocyte proportion and extensive fibrosis were identified as 25% and 20% respectively. Raised BAL lymphocyte proportion was rare in patients with a UIP pattern (8/135[5.9%]) or with extensive fibrosis (7/144[4.9%]). In the validation cohort (n=290 subjects), a raised BAL lymphocyte proportion was associated with a significantly lower probability of disease progression in patients with non-extensive fibrosis or a non-UIP pattern. BAL lymphocytosis is rare in patients with extensive fibrosis or a UIP pattern on CT. In patients without a UIP pattern or with limited fibrosis, a BAL lymphocyte proportion of ≥ 25% was associated with a lower likelihood of progression.