Crop rotation has several essential functions in organic vegetable production. Rotation is used to maintain soil productivity, to ensure sufficiency of nutrients and to manage pests, so as to provide the farmer with a sufficient income. Organic crop rotations are often of long duration, and different crop combinations, cultivation practices and timing patterns exist in abundance. As a consequence, studying crop rotations in the form of field experiments is inconvenient and expensive. The amount of weeds and composition of weed flora can be managed by careful choice of crop species, cultivation techniques and control measures during the rotation. Crop rotation models should be designed to intensify on the management of the most problematic weeds and to help in allocating the resources to those areas from which the highest benefit is expected. Sufficient supply of nutrients may be a problematic issue, particularly when composted manure is not available on the farm. It is important to retain the nutrients in plant residues for the next crop and simultaneously reduce nutrient losses. Knowledge gathered from short-time experiments can be utilised when nutrient balance and nutrient release rates in different crop rotations are evaluated. Calculations and estimates of labour requirement on the farm are needed for planning crop rotation, evaluating profitability or acquiring new machinery. With dynamic models it is possible to anticipate both annual and daily labour use, and accumulation of work. Only little research has been conducted on production costs and economy of organically grown horticultural crops. In crop rotation, the production costs of intermediate crops need also to be covered with the return gained from the vegetable crops. A sample economic calculation is presented on an organic crop rotation on a 25 ha farm with a six-year rotation. Even if the crop rotation is well planned in advance, unfavourable weather in spring or autumn and a changed market situation, among other things, may call for changes in the planned crop rotation. An annually prepared production plan updates the crop rotation plan to correspond to the changed situation.