objectives In India, frontline workers (FLWs)public accredited social health activists (ASHAs) and private rural medical providers (RMPs)are important for early detection and treatment of childhood diarrhoea and pneumonia. This cross-sectional study aims to measure knowledge and skills, and the gap between the two ('know-can' gap), regarding assessment of childhood diarrhoea with dehydration and pneumonia among FLWs, and to explore factors associated with them.methods We surveyed 473 ASHAs and 447 RMPs in six districts of Uttar Pradesh. We assessed knowledge and skills using face-to-face interviews and video vignettes, respectively, about key signs of both conditions. The 'know-can' gap corresponds to absent skills among FLWs with correct knowledge. We used logistic regression to identify the correlates of knowledge and skills.results FLWs' correct knowledge ranged from 23% to 48% for dehydration signs and 27% to 37% for pneumonia signs. Their skills ranged from 3% to 42% for dehydration and 3% to 18% for pneumonia. There was a significant 'know-can' gap in all the signs, except 'sunken eyes'. Training and supervisory support was associated with better knowledge and skills for diarrhoea with dehydration, but only better knowledge for pneumonia.conclusions FLWs are crucial to the Indian health system, and high-quality FLW services are necessary for continued progress against under-five deaths. The gap between FLWs' knowledge and skills warrants immediate attention. In particular, our results suggest that knowledge-focused trainings are insufficient for FLWs to convert knowledge into appropriate assessment skills. Tropical Medicine and International Health volume 25 no 4 pp 454-466 april 2020 L. Ray Saraswati et al. 'Know-can' gap among frontline workers in India 62.6 (56.1, 68.7) NA ASHA received training on ASHA module 60.4 (55.7, 64.9) NA Exposure and training on childhood diarrhoea management Received focused training on diarrhoea 51.0 (45.7, 56.4) 10.0 (5.3, 18.1) Presence of job-aid related to childhood diarrhoea management 52.5 (47.0, 58.0) 37.2 (28.3, 47.1) Received information about childhood diarrhoea from TV 55.2 (49.3, 60.9) 60.6 (50.5, 69.8) Received information about childhood diarrhoea from a government health worker 87.7 (83.9, 90.7) 39.8 (30.1, 50.4) Received information about childhood diarrhoea from a non-government health worker 17.9 (14.2, 22.4) 49.2 (38.8, 59.7) Personally seen at least one case of childhood diarrhoea in last 7 days 25.2 (20.5, 30.5) 52.2 (42.3, 61.9) Exposure and training on childhood pneumonia management: Received focused training on pneumonia 43.1 (37.6, 48.7) 8.3 (4.0, 16.6) Presence of job-aid related to childhood pneumonia management 33.2 (28.4, 38.4) 9.8 (4.2, 21.5) Received information about childhood pneumonia from TV 40.1 (34.9, 45.5) 59.1 (49.1, 68.4) Received information about childhood pneumonia from a government health worker 79.4 (73.9, 83.9) 31.8 (21.5, 44.3) Received information about childhood pneumonia from a non-government health worker 14.7 (11.0, 19.3) 46...