Frits Koster (1957) began practising insight meditation in 1979. He ordained as a Buddhist monk for six years, practising vipassana meditation and studying Buddhist scriptures in meditation centres and monasteries in Thailand and Burma. In 1988 he returned to the Netherlands, where he has been facilitating meditation retreats ever since. He disrobed, and now works part-time in psychiatric health care, as well as offering courses in Buddhist psychology and philosophy.

Frits has written several books. Three of these books have been translated into English: Liberating Insight (2004), Buddhist Meditation as Stress Management (2006) and The Web of Buddhist Wisdom (2015). These books are published by Silkwormbooks; see www.silkwormbooks.com for more information.

Frits is a teacher and trainer in Mindfulness-Based Stress Reduction (MBSR) and in Mindfulness-Based Cognitive Therapy (MBCT). As a trainer he is connected to mindfulness Teacher Training Institutes throughout Europe.

In 2015 Frits followed a Teacher Training (with Florence Meleo-Meyer & Phillis Hicks) and developed as an Interpersonal Mindfulness Program (IMP) teacher.

Together with psychiatrist Erik van den Brink he developed a follow-up programme for participants who have already followed a course in MBSR/MBCT. This programme is called Mindfulness-Based Compassionate Living (MBCL), which is taught throughout the world. Together they wrote Mindfulness-Based Compassionate Living (Routledge, 2015) and A Practical Guide to Mindfulness-Based Compassionate Living (Routledge, 2018). These books have been published in various languages.

With his wife Jetty Heynekamp he leads retreats in the Netherlands and abroad. Together they have written a book (in Dutch language) on the process of going on retreat; it is being translated into English. Together with Victoria Norton, they have edited Mindful Communication (Routledge, 2023), which describes six valuable mindfulness-based communication programmes.

Frits is now involved in developing a training programme on forgiveness with Joyce Cordus, it  is called Mindfulness-Based Training in Forgiveness (MBTF).